No Rolling Stone will have such a hanger-on (4)
I believe the answer is:
moss
'a hanger-on' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'no rolling stone will have' is the wordplay.
I cannot really understand how this works, but
'no' could be 'o' (O resembles 0) and 'o' is present in the answer.
The remaining letters 'mss' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'such' acts as a link.
Can you help me to learn more?
(Other definitions for moss that I've seen before include "Low-growing plant" , "Parasitic plant" , "Plant growing on many lawns" , "Clear < tiny plants" , "Stirling --, racing driver" .)