Once more leader ignored profit (4)
I believe the answer is:
gain
'profit' is the definition.
(I know that profit is a kind of gain)
'once more leader ignored' is the wordplay.
'once more' becomes 'again' (synonyms).
'leader ignored' means to remove the first letter.
'again' with its initial letter taken off is 'GAIN'.
(Other definitions for gain that I've seen before include "Earn, profit" , "reward" , "Advance" , "Profit; acquire" , "Pick up" .)