Dubious spasm on muscles rotating case of alcohol (9)
I believe the answer is:
sceptical
'dubious' is the definition.
(I've seen this before)
'spasm on muscles rotating case of alcohol' is the wordplay.
'spasm' becomes 'tic' (tic is a kind of spasm).
'on' means one lot of letters go next to another.
'muscles' becomes 'pecs' (short for pectoral muscles).
'rotating' says the letters should be written backwards.
'case of' suggests removing the centre (outsides of).
'alcohol' with its centre taken out is 'al'.
'pecs' in reverse letter order is 'scep'.
'tic' put after 'scep' is 'sceptic'.
'sceptic'+'al'='SCEPTICAL'
(Other definitions for sceptical that I've seen before include "Doubtful" , "Inclined not to believe" , "dubious" , "Inclined to doubt accepted opinions" , "Given to doubt" .)