Bird beginning to display comb (5)
I believe the answer is:
drake
'bird' is the definition.
(drake is a kind of bird)
'beginning to display comb' is the wordplay.
'beginning to' says to take the initial letters.
'comb' becomes 'rake' (I've seen this in another clue).
The first letter of 'display' is 'd'.
'd'+'rake'='DRAKE'
(Other definitions for drake that I've seen before include "Ship" , "Seaman" , "Aquatic bird" , "Elizabethan sailor" , "Male duck - circumnavigator" .)