Help with a wager? (4)
I believe the answer is:
abet
'help' is the definition.
(I've seen this before)
'with a wager?' is the wordplay.
'with' is a charade indicator (letters next to each other).
'wager?' becomes 'bet' ('bet' can be a synonym of 'wager').
'a' next to 'bet' is 'ABET'.
(Other definitions for abet that I've seen before include "Assist wrongly!" , "Crookedly endorse" , "Assist (in doing wrong?)" , "Incite (to commit an offence)" , "Help a criminal" .)