Ambassador at site organised pause (8)
I believe the answer is:
hesitate
'pause' is the definition.
(I know that pause can be written as hesitate)
'ambassador at site organised' is the wordplay.
'ambassador' becomes 'he' (His or Her Excellency).
'organised' is an anagram indicator.
'at'+'site'='atsite'
'atsite' is an anagram of 'sitate'.
'he'+'sitate'='HESITATE'
(Other definitions for hesitate that I've seen before include "Hold back in doubt" , "Be in two minds" , "Show indecision" , "Do this perhaps to be lost" , "Stall" .)