All for (3)
I believe the answer is:
pro
'all for' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pro that I've seen before include "In favour of; advantage" , "Professional; advantage" , "In brief, he's no amateur" , "Golf expert" , "One doesn't play just for the love of it, in short" .)