In Apple a US form of congratulations (8)
I believe the answer is:
applause
'form of congratulations' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'in apple a us' is the wordplay.
'in' indicates putting letters inside.
'a'+'us'='aus'
'apple' going around 'aus' is 'APPLAUSE'.
Can you help me to learn more?
(Other definitions for applause that I've seen before include "Noisy expression of approbation" , "Burst of clapping" , "Acclamation" , "Clapping US appeal?" , "Audible indication of approval or praise" .)