Not a genuine stone or stick (5)
I believe the answer is:
paste
'stick' is the definition.
(as in sticking or pasting something down)
'not a genuine stone' is the wordplay.
I cannot quite see how this works, but
'a' is present in the answer.
'stone' could be 'st' (abbreviation) and 'st' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'or' acts as a link.
Can you help me to learn more?
(Other definitions for paste that I've seen before include "sound beating" , "Fake gems; adhesive" , "food preparation" , "Watery cement" , "defeat" .)