Knothead with each bird (3)
I believe the answer is:
kea
'bird' is the definition.
(kea is a kind of bird)
'knothead with each' is the wordplay.
'knothead' becomes 'k' (head letter of 'knot').
'with' means one lot of letters go next to another.
'each' becomes 'ea'.
'k'+'ea'='KEA'
(Other definitions for kea that I've seen before include "Large New Zealand parrot" , "Green NZ parrot" , "NZ mountain parrot" , "NZ flyer" , "bird" .)