I would back Mum’s cooked Chinese dish (3,3)
I believe the answer is:
dim sum
'chinese dish' is the definition.
(I've seen this before)
'i would back mum's cooked' is the wordplay.
'i would' becomes 'I'd'.
'back' shows that the letters should be reversed in order.
'cooked' indicates anagramming the letters (letters cooked into a new form).
'id' reversed gives 'di'.
'mums' anagrammed gives 'msum'.
'di'+'msum'='DIM SUM'
(Other definitions for dim sum that I've seen before include "steamed dumplings" , "Chinese fare" , "Exotic food" , "something to take away?" , "Chinese dumpling dish" .)