Bird's short time with another heron (7)
I believe the answer is:
moorhen
'bird's' is the definition.
(moorhen is a kind of bird)
'short time with another heron' is the wordplay.
'short time' becomes 'mo' (slang abbreviation for 'moment').
'with' is a charade indicator (letters next to each other).
'another' indicates an anagram.
'heron' with letters rearranged gives 'orhen'.
'mo'+'orhen'='MOORHEN'
(Other definitions for moorhen that I've seen before include "Bird - hormone (anag)" , "Female red grouse or waterfowl" , "Black waterbird" , "Black freshwater bird" , "Medium-sized, blackish aquatic bird with long toes" .)