Duck into bed with a bird (4)
I believe the answer is:
coot
'bird' is the definition.
(I know that coot is a type of rail)
'duck into bed' is the wordplay.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'into' indicates putting letters inside.
'bed' becomes 'cot' (cot is a type of bed).
'o' placed into 'cot' is 'COOT'.
'with a' acts as a link.
(Other definitions for coot that I've seen before include "Blackish aquatic bird" , "Waterfowl" , "Waterbird of rail family" , "'Slow-flying, duck-like bird (4)'" , "Slow-flying bird, resembling a duck" .)