Sweet, strong tipple on the rocks? (9)
I believe the answer is:
liquorice
'sweet' is the definition.
(liquorice is a kind of sweet)
'strong tipple on the rocks?' is the wordplay.
'strong tipple' becomes 'liquor' (I can't explain this - if you can you should give a lot more credence to this answer).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'the rocks?' becomes 'ice' (both can informally mean diamonds).
'liquor'+'ice'='LIQUORICE'
Can you help me to learn more?
(Other definitions for liquorice that I've seen before include "Pontefract cake ingredient" , "Confectionary flavoured with root extract" , "Sweet" , "something black?" , "Strange flavour of a Rio clique" .)