Reprimand actors one found by entrance (9)
I believe the answer is:
castigate
'reprimand' is the definition.
(castigating is a kind of reprimanding)
'actors one found by entrance' is the wordplay.
'actors' becomes 'cast' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'found by' means one lot of letters go next to another.
'entrance' becomes 'gate' (I've seen this before).
'cast'+'i'+'gate'='CASTIGATE'
(Other definitions for castigate that I've seen before include "Chastise - tacit sage (anag)" , "Blast" , "Take a piece out of" , "Take to task" , "Severely criticise" .)