Piece of a blossom (5)
I believe the answer is:
petal
'piece of a blossom' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for petal that I've seen before include "Part of a plant's perianth that is usually brightly coloured" , "Small seal set in a ring" , "Corolla leaf" , "Floral segment" , "A bit of a bloomer" .)