Hormone transforms common bird (7)
I believe the answer is:
moorhen
'common bird' is the definition.
'moorhen' can be an answer for 'bird' (moorhen is a kind of bird). I'm not certain of the 'common' bit.
'hormone transforms' is the wordplay.
'transforms' is an anagram indicator (I've seen 'transformed' mean this).
'hormone' is an anagram of 'MOORHEN'.
Can you help me to learn more?
(Other definitions for moorhen that I've seen before include "pond bird" , "Female red grouse or waterfowl" , "Common aquatic bird" , "Medium-sized, blackish aquatic bird with long toes" , "Black waterbird" .)