Actually kind of harder than I am used to from this pair! Got a bit stumped here and there, but there was probably some element of luck involved.

Across

1

Give away large amount of red meat (6)
REVEAL — REd (large amount of red) VEAL (meat)

5

Sulphur in septic interfered with collection of waste (7)
CESSPIT — S (sulphur) inside anagram (interfered with) of SEPTIC

9

Mad Italian user maligned a local product endorsement (4,2,9)
MADE IN AUSTRALIA — anagram (maligned) of MAD ITALIAN USER

10

One who's dropped off fish with no head (6)
NAPPER — sNAPPER without first letter

11

A short time at home disrupted travel (8)
INTERVAL — IN (at home) anagram (disrupted) of TRAVEL

13

Tailored large suit and ties (9)
LIGATURES — anagram (tailored) of LARGE SUIT

15

Good-looker beginning with soul music (5)
SPUNK — S (first letter of soul) PUNK (music)

17

Calls up items in jeweller's inventory (5)
RINGS — double def.

19

Trade vehicle parking in front of way in (9)
CARPENTRY — CAR (vehicle) P (parking) ENTRY (way in)

21

Nicest ewes sprayed ahead of examination (8)
SWEETEST — anagram (sprayed) of EWES, then TEST (examination)

22

Gangster loves bad luck? (6)
HOODOO — HOOD (gangster) OO (loves)

25

Man, insincere, had translated language (8,7)
MANDARIN CHINESE — anagram (translated) of MAN INSINCERE HAD

26

Touch sea-bird, for example (7)
PATTERN — PAT (touch) TERN (sea-bird)

27

Energetic person recalled many in party (6)
DYNAMO — reversal (recalled) of MANY inside DO (party)

Down

2

Finish reproduction of nude sitting by piano (3,2)
END UP — anagram (reproduction) of NUDE, P (piano)

3

Noticeable form of identification worn in event (7)
EVIDENT — ID (form of identification) inside EVENT

4

Hang around Vienna, say (4)
LOAF — double def.

5

A son, kept in retreat by Castro, organised the mob (4,6)
COSA NOSTRA — A, reversal (in retreat) of SON inside anagram (organised) of CASTRO

6

Shows a movie trailer at the end in different scenes (7)
SCREENS — R (final letter of trailer) inside anagram (different) of SCENES

7

Athletic competition in European location that's secure (4,5)
POLE VAULT — POLE (European) VAULT (location that's secure)

8

Time to attack or hang back (5)
TRAIL — T (time) RAIL (to attack)

9

Butcher married fisherman (7)
MANGLER — M (married) ANGLER (fisherman)

12

Train senior cops going through reassignment (10)
PROCESSION — anagram (reassignment) of SENIOR COPS

14

Get urn boiling after drink and biscuit (6,3)
GINGER NUT — anagram (boiling) of GET URN after GIN (drink)

16

Opener's opening? (7)
KEYHOLE — &lit, KEY (opener) HOLE (opening)

18

At sea it wrecked stuff (7)
SATIATE — anagram (wrecked) of AT SEA IT

20

Number one book raised strong feeling (7)
EMOTION — reversal (raised) of NO (number) I (one) TOME (book)

21

Assess uranium found in engine's oil reservoir (3,2)
SUM UP — U (uranium) inside SUMP (engine's oil reservoir)

23

Imagine front of daily paper (5)
DREAM — D (first letter of daily) REAM (paper)

24

Sailed through section of rising tide carefully (4)
ACED — reversal (rising) of hidden (section of) tiDE CArefully