Bird beginning to seem pale (4)
I believe the answer is:
swan
'bird' is the definition.
(I know that Swan is a type of bird)
'beginning to seem pale' is the wordplay.
'beginning to' indicates taking the first letters.
'pale' becomes 'wan' (wan can mean pale or grey).
The initial letter of 'seem' is 's'.
's'+'wan'='SWAN'
(Other definitions for swan that I've seen before include "black, in 7th" , "Mute, whooper or Bewick's bird" , "possibly mute" , "Long-necked water bird" , "Whooper or trumpeter?" .)