I won't keep mum's provisions (4)
I believe the answer is:
nosh
'provisions' is the definition.
(both can mean food)
'i won't keep mum's' is the wordplay.
'i won't' becomes 'no' (refusal).
'keep mum' becomes 'sh' (both are ways of telling someone to be quiet).
'no'+'sh'='NOSH'
(Other definitions for nosh that I've seen before include "(Eat) a snack" , "A slang meal" , "Fare" , "Slangy food or meal" , "Food - eat greedily" .)