Coat with which a king dresses girl (6)
I believe the answer is:
anorak
'coat' is the definition.
(anorak is a kind of coat)
'a king dresses girl' is the wordplay.
'king' becomes 'k'.
'dresses' is an insertion indicator (dress can mean cover).
'girl' becomes 'nora' (**).
'a'+'k'='ak'
'ak' placed around 'nora' is 'ANORAK'.
'with which' is the link.
(Other definitions for anorak that I've seen before include "Coat (for the boringly obsessive?)" , "Zipped jacket with hood attached" , "Socially inept person" , "trainspotter" , "Boringly obsessive person" .)