Separate working gains edge (9)
I believe the answer is:
disengage
'separate' is the definition.
(I've seen this in another clue)
'working gains edge' is the wordplay.
'working' is an anagram indicator.
'gains'+'edge'='gainsedge'
'gainsedge' with letters rearranged gives 'DISENGAGE'.
(Other definitions for disengage that I've seen before include "free" , "Withdraw" , "Remove (troops) from a conflict" , "Separate, release, detach" .)