Plain person, perhaps Scarlett carries old man around (7)
I believe the answer is:
arapaho
'plain person' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'scarlett carries old man around' is the wordplay.
'scarlett' becomes 'ohara' (I've seen this in another clue).
'carries' means one lot of letters goes inside another (inserted letters carried inside).
'old man' becomes 'pa' (both can mean someone's father).
'around' says the letters should be written in reverse.
'ohara' placed around 'pa' is 'ohapara'.
'ohapara' reversed gives 'ARAPAHO'.
'perhaps' acts as a link.
Can you help me to learn more?
(Other definitions for arapaho that I've seen before include "Brave" , "North American Indian" , "tribe member" , "North American native" , "Indians" .)