Feathers found before defeat are gloomy (8)
I believe the answer is:
downbeat
'gloomy' is the definition.
(I've seen this in another clue)
'feathers found before defeat' is the wordplay.
'feathers' becomes 'down' (down can mean bird feathers).
'found before' means one lot of letters go next to another.
'defeat' becomes 'beat' (beating is a kind of defeating).
'down'+'beat'='DOWNBEAT'
'are' acts as a link.
(Other definitions for downbeat that I've seen before include "Gloomy; laid-back" , "Understated; gloomy" , "Conductor is likely to make this movement" , "Pessimistic; understated" , "Pessimistic, gloomy" .)