Adds with fingers (4)
I believe the answer is:
tots
This clue could be a double definition.
'adds' is the first definition.
('tot' can be a synonym of 'add')
'fingers' is the second definition.
The answer and definition can be both to do with communicating as well as being verbs in their -s form.
Maybe you can see an association between them that I can't see?
'with' is the link.
Can you help me to learn more?
(Other definitions for tots that I've seen before include "Finds the sum" , "little people" , "Adds up like small children" , "Little children" , "Babies" .)