Horror film taken in by tipsy choirboys (6)
I believe the answer is:
psycho
'horror film' is the definition.
(I've seen this before)
'taken in by tipsy choirboys' is the wordplay.
'taken in by' indicates the answer is hidden within the clue.
'PSYCHO' is hidden within 'tipsy choirboys'.
(Other definitions for psycho that I've seen before include "Nineteen sixty Hitchcock film" , "1960 Hitchcock film" , "Hitchcock classic" , "> fruitcake" , "Prefix denoting the mind or soul" .)