They can help make movies special (7)
I believe the answer is:
effects
'they can help' is the definition.
The definition suggests an adverb but the answer is not.
'make movies special' is the wordplay.
'make' becomes 'effect' (effecting is a kind of making).
'movies special' becomes 's' (I can't explain this - if you can you should believe this answer much more).
'effect'+'s'='EFFECTS'
Can you help me to learn more?
(Other definitions for effects that I've seen before include "They always have causes" , "Consequences or possessions" , "one's luggage" , "They follow causes" , "left by the dead" .)