Part of a small coin? (3)
I believe the answer is:
bit
This clue is a double definition.
'part' is the first definition.
(both mean a piece of something)
'a small coin?' is the second definition.
'of' acts as a link.
(Other definitions for bit that I've seen before include "Cutting head of a drill" , "Small piece; boring tool" , "Cutting piece of a drill (3)" , "Took effect - fragment" , "Unspoken" .)