Discipline Charles X (7)
I believe the answer is:
chasten
'discipline' is the definition.
(I've seen this in another clue)
'charles x' is the wordplay.
'charles' becomes 'Chas' (shortened form).
'x' becomes 'ten' (X is the Roman numeral for ten).
'chas'+'ten'='CHASTEN'
(Other definitions for chasten that I've seen before include "Subdue pride of with a stench" , "Punish, purify" , "Have a restraining effect on (someone)" , "Subdue, correct by punishing" , "Humble" .)