Bird's egg found in bed (4)
I believe the answer is:
coot
'bird's' is the definition.
(coot is a kind of bird)
'egg found in bed' is the wordplay.
'egg' becomes 'o' (I've seen this in other clues).
'found in' is an insertion indicator.
'bed' becomes 'cot' (cot is a kind of bed).
'o' inserted into 'cot' is 'COOT'.
(Other definitions for coot that I've seen before include "Waterfowl" , "'Bald' water bird" , "Aquatic bird of the rail family" , "Slow-flying bird, resembling a duck" , "Stupid or eccentric man" .)