Rough breeches worn by a king (6)
I believe the answer is:
hoarse
'rough' is the definition.
(I've seen this before)
'breeches worn by a king' is the wordplay.
'breeches' becomes 'hose' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'worn by' indicates putting letters inside (I've seen this in other clues).
'king' becomes 'r' (r is abbreviation for rex).
'a'+'r'='ar'
'hose' placed around 'ar' is 'HOARSE'.
Can you help me to learn more?
(Other definitions for hoarse that I've seen before include "'Husky, gruff (6)'" , "Hackney" , "Raucous" , "Having a frog" , "Ashore (anag)" .)