Water bird - an injured heron - put under the doctor (7)
I believe the answer is:
moorhen
'water bird' is the definition.
(I've seen this before)
'an injured heron put under the doctor' is the wordplay.
'an injured' indicates anagramming the letters.
'put under' means one lot of letters go next to another.
'the doctor' becomes 'mo' (medical officer).
'heron' is an anagram of 'orhen'.
'orhen' after 'mo' is 'MOORHEN'.
(Other definitions for moorhen that I've seen before include "Medium-sized, blackish aquatic bird with long toes" , "Water bird" , "Common aquatic bird" , "Bird - hormone (anag)" , "Female red grouse or waterfowl" .)