Sit awkwardly in ceremonial uniform in agony (8)
I believe the answer is:
distress
'agony' is the definition.
(thesaurus)
'sit awkwardly in ceremonial uniform' is the wordplay.
'awkwardly' is an anagram indicator.
'in' means one lot of letters goes inside another.
'ceremonial uniform' becomes 'dress'.
'sit' is an anagram of 'ist'.
'ist' inserted within 'dress' is 'DISTRESS'.
'in' is the link.
(Other definitions for distress that I've seen before include "State of anxiety or woe" , "Peril" , "Extreme anxiety or sorrow" , "Pain, trouble or sorrow" , "Unhappiness" .)