Flyer in another nest (4)
I believe the answer is:
erne
'flyer' is the definition.
(I've seen this before)
'in another nest' is the wordplay.
'in' says the answer is hidden in the clue.
'ERNE' can be found hidden inside 'another nest'.
(Other definitions for erne that I've seen before include "Sea-eagle in an Irish lake" , "Lough of the North" , "Marine flyer" , "'Sea-eagle, river and lough (4)'" , "Flier" .)