Fantastic beast's nose caught on gold ring at the start (7)
I believe the answer is:
centaur
'fantastic beast's nose' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'caught on gold ring at the start' is the wordplay.
'caught on' becomes 'cent' (I can't explain this - if you can you should give a lot more credence to this answer).
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'at the start' suggests taking the first letters.
The initial letter of 'ring' is 'r'.
'cent'+'au'+'r'='CENTAUR'
Can you help me to learn more?
(Other definitions for centaur that I've seen before include "Mythical animal, half man and half horse" , "Half-man and half horse" , "Mythical creature with horse's body and man's upper torso" , "Mythological creature" , "Fabulous horse-man" .)