The female got aboard with the flier (5)
I believe the answer is:
'the flier' is the definition.
(heron is a kind of birdanimal)
'the female got aboard' is the wordplay.
'the female' becomes 'her' (I've seen this before).
'got' is a charade indicator (letters next to each other).
'aboard' becomes 'on'.
'with' is the link.
(Other definitions for heron that I've seen before include "Rhone (anag) - bird" , "Large British wading bird" , "One bird" , "Wading bird with long neck and legs" , "Grey or white long-legged wading bird" .)