His Bolero might seem a bit of a marvel (5)
I believe the answer is:
ravel
This clue could be a double definition.
'his bolero might seem a bit' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'marvel' is the second definition.
The answer and definition can be both related to natural events as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'of a' is the link.
Can you help me to learn more?
(Other definitions for ravel that I've seen before include "Entangle - French composer, d. 1937" , "Bolero's composer" , "Tangle or become tangled" , "French composer, Maurice (1875-1937)" , "note-writer observed" .)