4035 Half a Dozen by Nibor

This was a nice tribute for Haydn’s bicentenary, appearing a week too early as the end of the month was reserved for the maths puzzle. The omitted letters gave “JOSEPH HAYDN DIED THIRTY-FIRST MAY EIGHTEEN-O-NINE”. The unclued entries were the jumbled forms of six of Haydn’s twelve London symphonies, SURPRISE, MIRACLE, MILITARY, CLOCK, DRUM ROLL and LONDON.

Letters omitted in clues are shown in []

Across
1 Large marine animal exhibiting loppy [J]udders (5)
POLYP Anagram LOPPY
11 Sco[O]t off for good to USA for instance - English plane has class (8)
EMIGRATE E + MIG + RATE
12 Former French copper, missing extremities, rever[S]ed shy people (4)
MICE (d)ECIM(e) reversed
13 Maybe Ripon and Exeter, for instance? [E]Yes! (4)
SEES 2 definitions
15 Body with internal temperature giving [P]ore for plant gases (5)
STOMA T in SOMA
16 [H]Ash in Scotland, a Norse god with sex appeal? Not half! (3)
ASS AS (Norse god) + S(a) (sex appeal)
17 [H]Owl swallows sick bat (6)
WILLOW ILL in WOW
19 One socially acceptable, backing co[A]t with solder (4)
UNIT U + TIN (reversed)
22 Dick[Y] rang for the heartless chap with property along the shore? (9)
FRONTAGER Anagram RANG FOR T(h)E
23 A little [D]evil publicity is perhaps unsuitable (6)
IMPAIR IMP + AIR
24 [N]Allah, a bishop and topless fool (6)
ARROYO A RR (Right Reverend) + (b)OYO
27 Bolt of cor[D]ed cloth spun round about (6)
SPERRE REPS (reversed) + RE
32 Disordered, without no[I]se, returning in very black kind of light (9)
BETUMBLED MUTE (reversed) in BB + LED
35 Excessive f[E]asting gets rid of random explosive energy (4)
GISM G(ormand)ISM less anagram RANDOM
37 [D]O, I vibrate, extremely liable to erupt (6)
ACTIVE ACT (do) + I + V(ibrat)E
38 Expression of surprise at old [T]railing round house (3)
OHO HO (house) reversed + O (old)
40 Greyish-brown clot[H] is a feature of recrudescence (4)
ECRU Hidden
41 To use ba[I]t to propel through tunnel? No good (4)
TOLE TO + LE(g) less G (good)
42 Almost d[R]unk the fellow reversing without having a proper look (8, three words)
ON THE NOD ON (almost drunk) + THE + DON (reversed)
43 Lower part in due[T] support of ... (7)
SECONDO SECOND + O (of)
44 ... step one celestial bod[Y] must take in (5)
STAIR I (one) in STAR
 
Down
2 Warning of what's to come when there's only the [F]air? (4)
OMEN O (zero) MEN
3 God saves beloved hero[I]n in sea, acceptable not base (6)
JOSHUA JO (beloved) + H in SEA less E (base) + U (acceptable)
4 Outlaw wife found in tangled co[R]pse (9)
PROSCRIBE RIB (wife) in Anagram CORPSE
5 Old plunderer gives boo[S]t to the old queen (6)
RAPTOR RAP + TO + R (queen)
6 Saw [T]an abandoned African people (6)
TSWANA Anagram SAW TAN
7 Laugh [M]asking Latin for yellow (4)
YOLK  L in YOK
8 This plant could be [A]rum, originally like ipomoea, liverwort and yarrow (4)
LILY first letters Like Ipomoea Liverwort Yarrow
9 With most of score, man[Y] devised shortened names (8)
ACRONYMS Anagram SCORE MANY
10 Gr[E]ater, to Ed's recurrent regret, can be used on the lawn (5)
MOWER MO (more) + REW (reversed)
14 Head la[I]d over at end of hike - a day's march (5)
ÉTAPE PATE (reversed) + (hik)E
18 Barbaric person did lin[G]er no good (3)
HUN HUNG less G
20 [H]Alf a foreigner takes the lid off boat races for the last parts of courses (9)
STRAIGHTS STRA(nger) + (e)IGHTS
21 [T]Weak arm, eg - ape to provide current strength (8)
AMPERAGE Anagram ARM EG APE
25 What will open out casement, close up rosace? It's what [E]vents do (5)
OCCUR first letters Out Casement Close Up Rosace
28 Time for deer's h[E]at, in truth (3)
RUT Hidden
29 Tailless mo[N]th at hospital department - it's used for a kind of purification (6)
ELUENT ELU(L) + ENT (Ear, Nose & Throat)
30 Po[O]le, perhaps half decayed supporting unproductive greenhouse? (6)
LEAN-TO LEAN (unroductive) + TO(wn)
31 State of being a co[N]y fashion designer endlessly in hostile environment (6)
IDIOCY DIO(r) in ICY
32 Faces unflinchingly d[I]ebs in disarray (5)
BIDES Anagram DIEBS
34 Spri[N]g for example used as part of antidepressant (4)
TIDE Hidden
36 Screaming with loss of [E]king as a title of respect (4)
SHRI SHRIEKING less EKING