Outlines number of starting markers of sun sign (9)

'outlines' 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?

'number of starting markers of sun sign' is the wordplay.
I cannot quite see how this works, but
'number' could be 'sum' (summing is a kind of numbering) and 'sum' is found within the answer.
'sun' could be 's' and 's' is found within the answer.
The remaining letters 'marie' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?