Bakery product — or part, so it’s said (4)
I believe the answer is:
roll
'bakery product' is the definition.
(I've seen this before)
'part so it's said' is the wordplay.
'part' becomes 'role' ('role' can be a synonym of 'part').
'so it's said' indicates a 'sounds like' (homophone) clue.
'role' sounds like 'ROLL'.
'or' is the link.
(Other definitions for roll that I've seen before include "start recording film" , "Move like a wheel" , "See 19" , "Furl" , "Official list of members" .)