Late bloomer, briefly behind (5)
I believe the answer is:
aster
'late bloomer' is the definition.
(I've seen this in another clue)
'briefly behind' is the wordplay.
'briefly' means to remove the last letter.
'behind' becomes 'astern' (at the back or behind of a ship).
'astern' with its last letter removed is 'ASTER'.
(Other definitions for aster that I've seen before include "Large daisy" , "Kind of daisy" , "Michaelmas daisy genus" , "Daisy-like garden flower" , "bloomer" .)