Heraldic beast (6)
I believe the answer is:
wyvern
'heraldic beast' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for wyvern that I've seen before include "Fabulous creature" , "Heraldic beast" , "1950s Vauxhall model" , "Winged two-legged dragon (heraldry)" , "Dragon with wings in medieval heraldry" .)