Spectators not allowed to finish show off (4)
I believe the answer is:
crow
'show off' is the definition.
'spectators not allowed to finish' is the wordplay.
'spectators' becomes 'crowd' (I've seen this before).
'not allowed to finish' means to remove the last letter.
'crowd' with its last letter taken away is 'CROW'.
(Other definitions for crow that I've seen before include "Express gleeful triumph" , "Brave" , "one often getting stoned!" , "Common bird" , "bar" .)