Maybe some bread roll found inside case (7)
I believe the answer is:
subunit
'maybe some' is the definition.
(a small unit of something)
'bread roll found inside case' is the wordplay.
'bread roll' becomes 'bun' (a bun is a bread roll).
'found inside' is an insertion indicator.
'case' becomes 'suit' (synonyms).
'bun' inserted inside 'suit' is 'SUBUNIT'.
(Other definitions for subunit that I've seen before include "Distinct component of something bigger" , "Constituent" .)