Riddles involving western birds (6)
I believe the answer is:
swifts
'birds' is the definition.
(swift is a kind of bird)
'riddles involving western' is the wordplay.
'riddles' becomes 'sifts' (I've seen this before).
'involving' indicates putting letters inside.
'western' becomes 'w'.
'sifts' going around 'w' is 'SWIFTS'.
(Other definitions for swifts that I've seen before include "Swallow-like birds" , "wingers" , "Small fast birds" .)