Lost clown fish of film (4)
I believe the answer is:
nemo
'lost clown fish of film' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nemo that I've seen before include "Literary captain" , "- me impune lacessit (motto of Scotland)" , "Jules Verne's submarine captain" , "Finding -, animated film" , "commander for the Nautilus" .)