4061 50-50 by Phi

To celebrate his fiftieth birthday Phi gave us one of his most difficult puzzles. A carte blanche grid, a lack of word lengths and 50-50 clues, where the wordplay belonged to a different clue, all contributed to the difficulty. The completed grid had two L-shaped parts (hence the title) and the “reflective symmetry” was in the two rectangles of the L-shapes. The word-length that only occurred in the larger L was 6-letter words. The initial letters of these clues gave SINGER. The three unclued names were all singers born in 1959, Suzanne Vega, Youssou N’Dour and Renee Fleming. The latter 2 being completely unknown to this Gregson!

In 50-50 clues explanations of wordplay are shown in [  ]

Across
Smears foreign country
PAYS 2 definitions (country in French)
Poet's to follow church or Lord, primarily
ENSEW [CEORL CE + OR + L(ord)]
African leader offering zero compensation for injury
OBOTE O + BOTE
Native of country in Soviet Asia
RUSS [ETAS Hidden]
WW1 soldier left in possession of weapon without force
ANZAC [RILLE L in RIFLE less F (force)]
Try it when time enables, primarily
TASTE ‘T (it) + AS (when) + T + E(nables)
Lures trapping black marine creature (two words)
SEA STAR [STABLES B IN stales]
Offensive player, drunk in shed (two words)
SPLIT END LIT (drunk) in SPEND
Part of calendar - first and third of August this year
ADAR [AGHA AuGust + HA (hoc anno)
Slave returned with freeman
CEORL [ENSEW ESNE reversed + W (with)
Unclued A NE VEGA
Notice fish egg container
OVULE [ADEEL AD + EEL]
Aware some aquarelles err when held up
SENTIENT [RESELLER Hidden reversed]
Spanish gent - a scoundrel in part
SEÑOR [PRATT RAT in PT (part)
Onion also chopped, without very much looking back
ESCHALOT [AEROSOLS SORE reversed in Anagram ALSO (here without means outside)]
Sexless parts are symbolic elements without function ultimately
ATOKES A (are) + TOKENS less (functio)N
Room-fresheners possibly dispersing the coals
AEROSOLS [ESCHALOTS Anagram THE COALS]
Miss getting cut, certainly, when receiving fashionable rejection
BRUSH-OFF [NINE-EYES NEE(d) containing IN (fashionable) + YES (certainly)]
Unclued B RENEE FLEMING
Implants those people at the forefront of the county
EMBEDS ‘EM (them) + BEDS (Bedfordshire)
Note number six about medicine is a letter
LAMEDH MED in LAH (6th note in sol-fa scale)
Increasingly bold set of notes left unfinished, along with one article
SASSIER [OCTAVIA OCTAV(e) + I + A
Excellent, and in the style of 20th century composer (two words)
DE FALLA DEF (excellent) + ALLA (in the style of)
 
Down
One company supporting style of living shown in range of columns
PORTICO PORT + I CO (company)
Get woken - music at dawn shifting you finally? That's about right
ABRADE AUBADE less (yo)U containing R
Unclued C YOUSSOU N’DOUR
Subsequent trader mailed it without most of final part
RESELLER [SENTIENT EN(d) in SENT IT]
Beauty costs, to eliminate first cause of poor tissue
ELASTASE [LOOKSEES LOOKS + (f)EES]
Primitive vertebrate slug eating reed
NINE-EYES [BRUSH OFF RUSH in BOFF]
Unclued A SUZANN
Characters in Greece cutting head from flowers on top of stem
ETAS [RUSS (t)RUSS]
Mark Antony's wife has sexual allure returning with uncontrollable rise
OCTAVIA [SASSIER ‘S (has) + SA reversed + Anagram RISE
Nothing against government losing leader? Just Arab guy
ADEEL [OVULE O + V (against) + (r)ULE]
Bottom individual's pulled back, right
PRATT [SEÑOR ONE’S reversed + R]
Bring down the rocks, interrupting layabout
DETHRONE Anagram THE in DRONE
Quick observations finally taken in peace
LOOKSEES [ELASTASE LAST in EASE]
Cavalryman's call to duty when in group artillerymen backed
STABLES [SEA STAR AS in SET + RA reversed]
Enlargement of gland must start to atrophy - doctor finally called in
STRUMA STUM + A(trophy) containing R (last letter of doctoR]
Repair one, involving hard decorative painting
MEHNDI H (hard) in MEND I
Scare old European in middle of safari
AFEAR E (European) in (s)AFAR(i)
Swore Spain's supplied after France
EFFED E (Spain) + F (France) + FED
A canal around about unknown feature on Mars
RILLE [ANZAC A + CAN reversed containing Z (unknown)
Treatise turning up in Fitzwilliam Museum
SUMMA Hidden reversed
Work that is produced by nursery rhyme specialist
OPIE OP (work) + IE (that is) ref. Iona & Peter Opie
Tennis player to advance onto line
LENDL LEND + L (line)
US women's organisation's after a chief officer
AGHA chief officer [ADAR A + DAR (Daughters of the American Revolution)