Support in a wager (4)
I believe the answer is:
abet
'support' is the definition.
(I've seen this in another clue)
'a wager' is the wordplay.
'wager' becomes 'bet' (synonyms).
'a'+'bet'='ABET'
'in' is the link.
(Other definitions for abet that I've seen before include "Criminally endorse" , "Assist criminally" , "Beat up by way of help" , "Help to do something wrong" , "Aid and help, perhaps in crime" .)