Flag bringing race to premature end (4)
I believe the answer is:
iris
'flag' is the definition.
(type of iris flower)
'race to premature end' is the wordplay.
'race' becomes 'irish' (I've seen this before).
'to premature end' means to remove the last letter (the word finishes early).
'irish' with its last letter taken off is 'IRIS'.
'bringing' is the link.
(Other definitions for iris that I've seen before include "is 21[WOMAN], perhaps" , "--- Murdoch, author" , "Goddess of the rainbow in the eye" , "Flag - part of eye" , "Murdoch in writing" .)