Disreputable yob, revolutionary for short time (6)
I believe the answer is:
louche
'disreputable' is the definition.
(similar in meaning)
'yob revolutionary for short time' is the wordplay.
'yob' becomes 'lout' (both can mean an antisocial young man).
'revolutionary' becomes 'Che' (Che Guevara the Marxist revolutionary).
'for short' suggests deleting specific letters (the word lacks or is short of certain letters).
'time' becomes 't' (abbreviation).
'lout'+'che'='loutche'
'loutche' with 't' taken away is 'LOUCHE'.
(Other definitions for louche that I've seen before include "Seedy" , "Shifty or disreputable" , "Shasy or questionable, from France" , "Raffish" , "Questionable or shady, from French" .)