Rickman of the Potter films (4)
I believe the answer is:
alan
'rickman of the potter films' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for alan that I've seen before include "A.A. Milne's first name" , "Messrs Ladd and Dukes" , "- Ayckbourn, English playwright" , "-- Turing, mathematician" , "-- Turing, English computer scientist" .)