Delay His Excellency -- one in government (8)
I believe the answer is:
hesitate
'delay' is the definition.
(hesitating is a kind of delaying)
'his excellency one in government' is the wordplay.
'his excellency' becomes 'he'.
'one' becomes 'i' (Roman numeral).
'in' means one lot of letters goes inside another.
'government' becomes 'state' (state is a kind of government).
'i' placed within 'state' is 'sitate'.
'he'+'sitate'='HESITATE'
(Other definitions for hesitate that I've seen before include "Pause in doubt, show uncertainty" , "Be uncertain about decision" , "Stall" , "Vacillate" , "'Pause, dither (8)'" .)