Open conversation with most of 1 across and half the town in 13 across
I believe the answer is:
heart-to-heart
'open' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for heart-to-heart that I've seen before include "Intimate talk" , "Candid conversation" , "Intimate conversation" .)