Ring bearer, at the end a monster (7)
I believe the answer is:
chimera
'monster' is the definition.
(I know that Chimera is a type of mythical creature)
'ring bearer at the end a' is the wordplay.
'ring' becomes 'chime' (eg a bell chimes or rings).
'at the end' says to take the final letters.
The final letter of 'bearer' is 'r'.
'chime'+'r'+'a'='CHIMERA'
(Other definitions for chimera that I've seen before include "Mythical creature; delusion" , "fake image" , "Illusory goal; monster" , "Mythical monster, part lion, goat and serpent" , "Mythological animal; something illusory" .)