Favouring a bit of an effort (3)
I believe the answer is:
for
'favouring' is the definition.
(to be 'for' something is to be in favour of it)
'a bit of an effort' is the wordplay.
'a bit of' says the answer is hidden in the clue.
'FOR' is hidden within 'effort'.
(Other definitions for for that I've seen before include "In support of" , "On the side of" , "On behalf of" , "Favouring" , "In favour of; since" .)