Roll touching substance that's dubious (8)
I believe the answer is:
register
'roll' is the definition.
(I've seen this in another clue)
'touching substance that's dubious' is the wordplay.
I cannot really see how this works, but
'touching' could be 're' (both can mean concerning or relating to) and 're' is located in the answer.
'substance' could be 'gist' (synonyms) and 'gist' is found within the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for register that I've seen before include "Official list or record" , "Index" , "Log" , "a manner of speaking" , "See 1" .)