Tick off one in the middle of scandal involving actors? (9)
I believe the answer is:
castigate
'tick off' is the definition.
(thesaurus)
'one in the middle of scandal involving actors?' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in the middle of' indicates putting letters inside.
'scandal involving actors?' becomes 'castgate' (castgate could mean a scandal involving a cast).
'i' going into 'castgate' is 'CASTIGATE'.
(Other definitions for castigate that I've seen before include "Berate" , "Censure severely" , "Take to task" , "Chastise - tacit sage (anag)" , "Severely criticise" .)