Petty case of sarcasm unsurpassed (5-4)
I believe the answer is:
small time
'petty' is the definition.
(I've seen this before)
'case of sarcasm unsurpassed' is the wordplay.
'case of' suggests removing the centre (outsides of).
'unsurpassed' becomes 'all-time' (I've seen this before).
'sarcasm' with its middle taken out is 'sm'.
'sm'+'alltime'='SMALL-TIME'
(Other definitions for small time that I've seen before include "Petty (criminal, usually)" , "Minor (colloq.)" , "Unimportant, minor" , "Unimportant (slang)" , "Mo may be so" .)