Savoury snack in packs, strong and rich when crunched (4,11)
I believe the answer is:
pork scratchings
'savoury snack' is the definition.
(type of snack)
'packs strong and rich when crunched' is the wordplay.
'and' is a charade indicator (letters next to each other).
'when crunched' indicates an anagram (letters crunched or scrunched up).
'packs'+'strong'+'rich'='packsstrongrich'
'packsstrongrich' is an anagram of 'PORK SCRATCHINGS'.
'in' acts as a link.
(Other definitions for pork scratchings that I've seen before include "local delicacy" , "bar snack" , "snacks" .)