Heraldic beast with very peculiar name (6)
I believe the answer is:
wyvern
'heraldic beast' is the definition.
(I've seen this before)
'with very peculiar name' is the wordplay.
'with' becomes 'w' (abbreviation**).
'peculiar' indicates anagramming the letters.
'name' becomes 'n' (common abbreviation e.g. on forms).
'very' anagrammed gives 'yver'.
'w'+'yver'+'n'='WYVERN'
(Other definitions for wyvern that I've seen before include "1950s Vauxhall model" , "In heraldry, a dragon with wings, two legs and a barbed tail" , "Heraldic form of dragon" , "Fabulous creature" , "Fire-breathing dragon with a snake's tail" .)