After joint, do giggle (4)
I believe the answer is:
jape
'giggle' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe there's a link between them I don't understand?
'after joint do' is the wordplay.
'after' says to put letters next to each other.
'joint' becomes 'j' (this might be a standard abbreviation of which I'm unaware).
'do' becomes 'ape' (both can mean to impersonate).
'j' next to 'ape' is 'JAPE'.
Can you help me to learn more?
(Other definitions for jape that I've seen before include "Lark" , "Trick - joke - jest" , "Kid" , "Jolly wheeze" , "Practical joke, jest" .)