Stones, 3 slowing down musically (4)
I believe the answer is:
grit
'stones 3' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'slowing down musically' is the wordplay.
I cannot really see how this works, but
'slowing down' could be 'rit' (abbreviation for musical term ritardando) and 'rit' is present in the answer.
A single letter 'g' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for grit that I've seen before include "Indomitability" , "Gravel or colloquial courage" , "Determination - which is found on winter roads" , "Persevering courage" , "Courage; tiny stones" .)