Frank —, director of five films in the St Trinian's series between 1954-80 (7)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
launder
(Other definitions for launder that I've seen before include "Act illegally" , "Make illegal (money) legitimate" , "Cleanse (material or money)" , "Perhaps decriminalise" , "Arundel (anag.)" .)