Ham producer allows seconds in for a feed (4)
I believe the answer is:
nosh
'for a feed' is the definition.
'ham producer allows seconds' is the wordplay.
I cannot really see how this works, but
'seconds' could be 's' and 's' is found in the answer.
The remaining letters 'noh' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'in' is the link.
(Other definitions for nosh that I've seen before include "Eat (slang) -- food (slang)" , "Eats" , "(Eat) a snack" , "chow" , "Food (coll)" .)