Ambassador in sight finding guillotine (6)
I believe the answer is:
behead
'guillotine' is the definition.
(I've seen this in another clue)
'ambassador in sight' is the wordplay.
'ambassador' becomes 'HE' (His or Her Excellency).
'in' is an insertion indicator.
'sight' becomes 'bead' (bead can mean a sight on a gun).
'he' inserted into 'bead' is 'BEHEAD'.
'finding' is the link.
(Other definitions for behead that I've seen before include "Execute on the block" , "Remove the crown" , "Guillotine" , "Decapitate" , "Knock one's block off!" .)