Good composer in small rock group (6)
I believe the answer is:
gravel
'small rock group' is the definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'good composer' is the wordplay.
'good' becomes 'g' (abbreviation).
'composer' becomes 'Ravel' (Maurice Ravel).
'g'+'ravel'='GRAVEL'
'in' is the link.
Can you help me to learn more?
(Other definitions for gravel that I've seen before include "Mixture of small stones" , "bits of rock" , "Small fragments of rock" , "Stone mixture for paths" , "Rock fragments and pebbles" .)