Trick diplomacy into touch (7)
I believe the answer is:
contact
'touch' is the definition.
(I know that touch can be written as contact)
'trick diplomacy' is the wordplay.
'trick' becomes 'con' (a con is a fraud or trick).
'diplomacy' becomes 'tact' (tact can mean diplomacy or sensitivity).
'con'+'tact'='CONTACT'
'into' acts as a link.
(Other definitions for contact that I've seen before include "Get in touch with" , "Close interaction" , "Approach" , "Useful acquaintance" , "state of one exposed to disease" .)