Parts may be used as bait (5)
I believe the answer is:
sprat
'as bait' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'parts may be' is the wordplay.
'may be' indicates anagramming the letters.
'parts' with letters rearranged gives 'SPRAT'.
'used' acts as a link.
Can you help me to learn more?
(Other definitions for sprat that I've seen before include "Traps (anag.)" , "Herring of the east North Atlantic" , "Small herring, often smoked or canned" , "Small marine fish" , "Herring's smaller relative" .)