Ploy to get one caught following diplomacy (6)
I believe the answer is:
tactic
'ploy' is the definition.
(thesaurus)
'one caught following diplomacy' is the wordplay.
'one' becomes 'i' (Roman numeral).
'caught' becomes 'c' (cricket abbreviation).
'following' is a charade indicator (letters next to each other).
'diplomacy' becomes 'tact' (I've seen this before).
'i'+'c'='ic'
'ic' after 'tact' is 'TACTIC'.
'to get' acts as a link.
(Other definitions for tactic that I've seen before include "Device" , "Action aimed at a specific end" , "Manoeuvre designed to outwit enemy" , "Plan, manoeuvre" , "Manoeuvre, stratagem" .)