There's nothing in the boxes but drawings (8)
I believe the answer is:
cartoons
'drawings' is the definition.
The answer and definition can be both related to communication as well as being plural nouns.
Perhaps you can see a link between them that I can't see?
'there's nothing in the boxes' is the wordplay.
'there's nothing' becomes 'o' (I've seen this in other clues).
'in the' means one lot of letters goes inside another.
'boxes' becomes 'cartons' (carton is a kind of box).
'o' inserted within 'cartons' is 'CARTOONS'.
'but' is the link.
Can you help me to learn more?
(Other definitions for cartoons that I've seen before include "Humorous or satirical drawings" , "Comic drawings, may be animated" , "Amusing and often pointed drawings in newspapers" , "Animated films or humorous drawings" .)