Punish Charles for a half-score (7)
I believe the answer is:
chasten
'punish' is the definition.
(chasten could historically mean to punish)
'charles for a half-score' is the wordplay.
'charles' becomes 'Chas' (shortened form).
'for' says to put letters next to each other.
'a half-score' becomes 'ten' (I've seen this in another clue).
'chas'+'ten'='CHASTEN'
(Other definitions for chasten that I've seen before include "Punish, purify" , "Suppress" , "Castigate or punish" , "Subdue pride of with a stench" , "Subdue - a stench (anag)" .)