26 across
Shooting
with
negative,
then
positive,
results
(13)
Shooting with negative, then positive, results (13)
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The whole clue is the definition (& lit or double definition).
How the clue works
The whole clue works as a cryptic definition — "shooting" gives you the surface sense of action, but the real nudge is that photographing is a kind of shooting that produces first a negative, then a positive print. There's no letter-by-letter wordplay here; the clue's just painting a cheeky picture of what the process actually involves.