Severe card about performing Scot (9)
I believe the answer is:
draconian
'severe' is the definition.
(I've seen this before)
'card about performing scot' is the wordplay.
'about' shows that the letters should be reversed in order.
'performing' becomes 'on' (as in being on stage).
'scot' becomes 'ian'.
'card' back-to-front is 'drac'.
'drac'+'on'+'ian'='DRACONIAN'
(Other definitions for draconian that I've seen before include "Cruel" , "Hard" , "Excessively severe" , "Very strict" , "Very harsh like severe laws" .)