String in compact edition did its job (5)
I believe the answer is:
Here is my best explanation:
'did its job' is the definition.
'string in compact edition' is the subsidiary indication.
'string in' indicates a hidden word.
'acted' is hidden within '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", "Played a role", "Appeared in play", "Play a role", "Performed on stage" and "Behaved or performed".)