Castle flyer (4)
I believe the answer is:
rook
I believe this is a double definition.
'castle' is the first definition.
(I know that castle can be written as rook)
'flyer' is the second definition.
(rook is a type of bird)
(Other definitions for rook that I've seen before include "Chess piece also called castle" , "Another name for castle in chess" , "Castle -- bird" , "Poignant, evocative" , "Rip off - bird" .)