Snack in foil, say pig's foot (6,3)
I believe the answer is:
scotch egg
'snack' is the definition.
(I've seen this before)
'foil say pig's foot' is the wordplay.
'foil' becomes 'scotch' (synonyms).
'say' becomes 'eg'.
'foot' indicates one should take the final letters (in a down clue, the bottom letter).
The last letter of 'pig' is 'g'.
'scotch'+'eg'+'g'='SCOTCH EGG'
'in' is the link.
(Other definitions for scotch egg that I've seen before include "Savoury snack" , "Picnic food" , "One cased in sausage meat" , "Snack, mostly breaded sausage meat" , "It is encased in sausage meat" .)