Conservative diplomacy leads to communication (7)
I believe the answer is:
contact
'communication' is the definition.
(contact is a kind of communication)
'conservative diplomacy' is the wordplay.
'conservative' becomes 'con' (abbreviation for Conservative).
'diplomacy' becomes 'tact' (tact can mean diplomacy or sensitivity).
'con'+'tact'='CONTACT'
'leads to' is the link.
(Other definitions for contact that I've seen before include "Communication" , "Talk to" , "Juxtaposition" , "Useful acquaintance" , "Get in touch with" .)