Spies pulling up some test negatives... (6)
I believe the answer is:
agents
'spies' is the definition.
(secret agents)
'pulling up some test negatives' is the wordplay.
'pulling up' is a reversal indicator.
'some' indicates a hidden word (some parts of the word are used).
'stnega' can be found hidden inside 'test negatives'.
'stnega' written backwards gives 'AGENTS'.
(Other definitions for agents that I've seen before include "They act for others" , "Instruments" , "Spies" , "They do business on behalf of others" , "Sales reps" .)