A chance to help (4)
I believe the answer is:
abet
'to help' is the definition.
(I've seen this before)
'a chance' is the wordplay.
'chance' becomes 'bet' (I've seen this in other clues).
'a'+'bet'='ABET'
(Other definitions for abet that I've seen before include "Urge on, help" , "helpful" , "Assist illegally" , "Give aid to" , "Beat up by way of help" .)