Disciplined impression at first, cast off after joke (8)
I believe the answer is:
punished
'disciplined' is the definition.
('punished' can be similar in meaning to 'disciplined')
'impression at first cast off after joke' is the wordplay.
'at first' says to take the initial letters.
'cast off' becomes 'shed' ('shed' can be a synonym of 'cast off').
'after' means one lot of letters go next to another.
'joke' becomes 'pun' (punning is a kind of joking**).
The initial letter of 'impression' is 'i'.
'i'+'shed'='ished'
'ished' put after 'pun' is 'PUNISHED'.
(Other definitions for punished that I've seen before include "penalised" , "grounded perhaps?" , "Impose a penalty on" , "Maybe flogged" , "Imposed a penalty" .)