That man makes speech in ceremonial caps (11)
I believe the answer is:
headdresses
'ceremonial caps' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps there's a link between them I don't understand?
'that man makes speech in' is the wordplay.
'that man' becomes 'he' ('he' refers to a man).
'makes' becomes 'se' (I can't justify this - if you can you should believe this answer much more).
'speech' becomes 'address' (address is a kind of speech).
'in' indicates putting letters inside.
'se' going into 'address' is 'addresses'.
'he'+'addresses'='HEADDRESSES'
Can you help me to learn more?
(Other definitions for headdresses that I've seen before include "ceremonial attire" , "Top Gear items?" .)