Mother’s put in limitless cumin for flavour (5)
I believe the answer is:
umami
'for flavour' is the definition.
(umami is one of the main taste categories)
'mother's put in limitless cumin' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'put in' is an insertion indicator.
'limitless' means to look at the middle letters.
The central letters of 'cumin' are 'umi'.
'ma' going into 'umi' is 'UMAMI'.
(Other definitions for umami that I've seen before include "meaty taste" , "Savoury taste sensation produced by glutamates - I, a mum (anag)" , "Newly discovered taste" , "Japanese word for pleasant savoury taste" , "Fifth flavour" .)