3994: 40 by Zero

Zero gave us a nice puzzle which was quite easy to complete. The unclued 40 gave us SPACE INVADERS and to complete the puzzle two letters had to be forced into a single cell. When these thematic cells were highlighted they formed the shape of a space invader from the video game which marks its 30th anniversary this year. There were some original clues and neat cryptic definitions. Gregson had to smile at the definition of LAP DANCERS.

ACROSS
1 Old chap working the ranch to fill break in mine work
PITHECANTHROPUS Anagram THE RANCH in PIT OPUS
10 Croatia not remaining in thrall for long
TALL THRALL less HR (Croatia)
12 Spotted American orchestra's leader making appearance in beat combo?
BAUSOND US + O(rchestra) in BAND
13 At heart, Aeneas seems desperate for unattainable goals
NEMESES Anagram NE (central letters of Aeneas) + SEEMS
14 One capturing a flat region in America, there for the taking (three words)
ON A PLATE A PLAT in ONE
15 Musical piece in E (possibly duet)
ETUDE E + anagram DUET
17 Czech Republic joining forces with Arabian ruler
CZAR CZ + AR
18 Rector's cutting to leave out selected passage
EXCERPT R (Rector) in EXCEPT
20 Ceremonial chamber's gallery claimed by returning North Africans
STATEROOM TATE (ref. Tate Gallery) in MOORS (reversed)
23 Inclination of Sri Lanka harvest folk to take in last of tea
CLINAMEN IN + (te)A in CL MEN
24 Departs, following letter about altered course
VEERED VEE + RE (about) + D (departs)
25 Jock's to go south across water to get shoes
GALOCHES GAE + S containing LOCH
27 Movers and shakers, lacking kit, apparently died in custody of soldiers (two words)
LAP DANCERS LANCERS containing AP (apparently) + D
29 Let the sun shine on number held in quarantine?
INSOLATE N (number) in ISOLATE
31 Curse dwelling in Cheshire village
EVIL Hidden
33 Way to reinstate covering note
STREET RE (note) in STET
34 Stab left-leaning peer
PINK 3 definitions
36 Telegram that might have made Fidel wait for co-ordination compound?
CHELATE ref. telegram from Che Guevara to Fidel Castro – Che late!
38 Showy pleasure building with piano and a violin playing
PAVILION Anagram P + A VIOLIN
39 Beings taking stick from rats, etc
ENTIA RODENTIA less ROD
DOWN
1 Tentatively writes up memo (enclosed within)
PENCILS SLIP reversed, containing ENC
2 Spanish woman's magazine (50 per cent recycled)
INEZ Anagram (maga)ZINE
3 Monkey deserted tropical tree
TAMARIND TAMARIN + D (deserted)
4 Abandoned these promises a long time ago
HETES Anagram THESE
5 Increase in heat provided by fusion; oxygen is not required
CALESCENCE COALESCENCE less O (oxygen)
6 Protozoan primarily found beneath northern river, not spring
NEAP N + EA (river) + P(rotozoan) (ref. NEAP TIDE)
7 Elevated French holding upper class in loathing
HAUTE U in HATE
8 Increased central lottery prize
ROSETTE ROSE + (lo)TTE(ry)
9 Reverses in United Nations -- peacemakers deprived of victory
UNDOES UN + DOVES less V
11 Independent person's fifty pound note
LONER L (50) + ONER
12 Damaged by bombs, Britain survived
BLASTED B + LASTED
16 Mechanical engineer comes up with problems -- no supporting devices
EMBLEMS ME (rev.) + PROBLEMS less PRO (supporting)
18 Cut back marks for test
EXAM AXE (reversed) + M (marks)
19 With this pigment, amateur might become painter
PTERIN anagram PAINTER less A (amateur)
21 Grace interrupted at regular intervals by one empty cat signalling lack of milk
AGALACTIA AGLAIA (one of the Graces) with A C(a)T
22 Place of vice in corrupt core of French town
ROCHELLE HELL in anagram CORE
23 Friend up in court on criminal charge that's nonsense
CLAPTRAP PAL reversed in CT (court) + RAP
24 Disinclination to dispense with a particular embodiment
VERSION AVERSION less A
26 See and note ancient jujube tree?
LOTE LO + TE
28 Soothing drug carried by old mountebank
ANETIC E (drug) in ANTIC
30 Poles receive sanction for former legal district
SOKEN OKE in SN (poles)
32 Flyer's not a traveller
VIATOR AVIATOR less A
34 Confusion about line dance move
PLIÉ L (line) in PIE
35 Letter to rabbi's sister
NUN 2 definitions (Hebrew letter)
37 Loaf about in first term of higher education
HEAD A (about) in H. Ed.