A weather-beaten bird (8)
I believe the answer is:
wheatear
'bird' is the definition.
(wheatear is a kind of bird)
'a weather-beaten' is the wordplay.
'beaten' indicates anagramming the letters (letters beaten up or destroyed).
'a'+'weather'='aweather'
'aweather' is an anagram of 'WHEATEAR'.
(Other definitions for wheatear that I've seen before include "singer" , "Songbird" , "Migrant's passion" , "bird" .)