Some ambitious editor exploited (4)
I believe the answer is:
used
'exploited' is the definition.
('used' can be a synonym of 'exploited')
'some ambitious editor' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'USED' can be found hidden inside 'ambitious editor'.
(Other definitions for used that I've seen before include "exhausted" , "Exploited group" , "Second-hand; exploited" , "Pre-owned" , "not got directly" .)