Fragment of bread (5)
I believe the answer is:
crumb
'fragment of bread' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for crumb that I've seen before include "Small bit (of comfort?)" , "Tiny piece of bread or cake" , "A shred of bread" , "tiny amount" , "Very small quantity of something, especially food" .)