String in compact edition did its job (5)
I believe the answer is:
acted
'did its job' is the definition.
'string in compact edition' is the wordplay.
'string in' indicates the answer is hidden within the clue.
'ACTED' can be found hidden inside 'compact edition'.
(Other definitions for acted that I've seen before include "Behaved like thespian" , "participated in panto maybe" , "Feigned" , "Took part in play" , "Behaved in a certain manner" .)