Said it's part bread (4)
I believe the answer is:
roll
'bread' is the definition.
(roll is a kind of bread)
'said it's part' is the wordplay.
'said' shows a homophone (sound like).
'it's part' becomes 'role' (eg a theatrical role).
'role' is a homophone of 'ROLL'.
(Other definitions for roll that I've seen before include "one filled at lunchtime, perhaps" , "Eg, bap" , "Cylinder (of paper etc)" , "start recording film" , "Official list; cylinder" .)