In movies, they're often special (7)
I believe the answer is:
effects
'in movies' is the definition.
The definition and answer can be both related to communication as well as being plural nouns.
Maybe they are linked in a way I don't understand?
'often special' is the wordplay.
I cannot quite see how this works, but
'special' could be 's' (common abbreviation as in Special Air Service) and 's' is present in the answer.
The remaining letters 'effect' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'they're' acts as a link.
Can you help me to learn more?
(Other definitions for effects that I've seen before include "Results - or properties" , "They follow causes" , "Personal belongings" , "goods" , "one's luggage" .)