Lists of numbers, in a popular sense (6)
I believe the answer is:
charts
'lists of numbers in a popular sense' is the definition.
The answer and definition can be both related to communication as well as being plural nouns.
Maybe they are linked in a way I don't understand?
'lists of numbers in' is the wordplay.
'lists of' becomes 'hart' (I can't justify this - if you can you should believe this answer much more).
'numbers' becomes 'Cs' (C is an example).
'in' is an insertion indicator.
'hart' placed within 'cs' is 'CHARTS'.
Can you help me to learn more?
(Other definitions for charts that I've seen before include "Maps to aid navigation" , "Sheets of tables, graphs or diagrams" , "Blueprints" , "Maps for captains" , "Maps for ship's captain" .)