One failing to win in close race (5)
I believe the answer is:
loser
'one failing to win' is the definition.
'in close race' is the wordplay.
'in' says the answer is hidden in the clue.
'LOSER' can be found hidden inside 'close race'.
(Other definitions for loser that I've seen before include "A failure, also-ran" , "One who frequently fails (colloq.)" , "Someone who fails consistently" , "Roles for the defeated" , "Failed competitor" .)