Capital display made by ambassador with speech (9)
I believe the answer is:
headdress
'capital display' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'ambassador with speech' is the wordplay.
'ambassador' becomes 'he' (His or Her Excellency).
'with' says to put letters next to each other.
'speech' becomes 'address' (synonyms).
'he'+'address'='HEADDRESS'
'made by' is the link.
Can you help me to learn more?
(Other definitions for headdress that I've seen before include "(Ceremonial) hat" , "capital cover" , "Top cover" , "top gear" , "Plumed helmet" .)