Staff's first sign of split with tons leaving (4)
I believe the answer is:
clef
'staff's' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for clef that I've seen before include "Symbol written on sheet music to indicate pitch" , "Symbol on stave in musical score" , "Staff symbol" , "Symbol at start of stave" , "Sign at start of stave" .)