Such figures are not Roman (6)
I believe the answer is:
arabic
'not roman' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'such figures are' is the wordplay.
I cannot quite understand how this works, but
'are' could be 'a' (the 'are' is a metric unit of area) and 'a' is found in the answer.
The remaining letters 'rabic' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for arabic that I've seen before include "foreign language" , "Correspond; last word of Othello" , "Language (of numbers)" , "There's a CIA bar on this language, oddly" , "Major language of Middle East" .)