Speech given by duke wearing a robe (7)
I believe the answer is:
address
'speech' is the definition.
(address is a kind of speech)
'duke wearing a robe' is the wordplay.
'duke' becomes 'd' (abbreviation).
'wearing' is an insertion indicator.
'robe' becomes 'dress' (I've seen this before).
'a'+'dress'='adress'
'd' placed inside 'adress' is 'ADDRESS'.
'given by' is the link.
(Other definitions for address that I've seen before include "Place of abode" , "particular house" , "Give a speech to" , "Where one lives" , "directions in window" .)