Undamaged during diplomacy (6)
I believe the answer is:
intact
'undamaged' is the definition.
(thesaurus)
'during diplomacy' is the wordplay.
'during' becomes 'in' (I've seen this in other clues).
'diplomacy' becomes 'tact' (I've seen this before).
'in'+'tact'='INTACT'
(Other definitions for intact that I've seen before include "Undamaged, unimpaired" , "Inviolate" , "Unbroken and unimpaired" , "Unbroken - sound" , "Entire and whole" .)