Decorate a foul docked boat (8)
I believe the answer is:
trimaran
'docked boat' is the definition.
'trimaran' can be an answer for 'boat' (thesaurus). I'm not sure about the 'docked' bit.
'decorate a foul' is the wordplay.
'decorate' becomes 'trim' (trimming is a kind of decorating).
'a foul' becomes 'aran' (I can't explain this - if you can you should give a lot more credence to this answer).
'trim'+'aran'='TRIMARAN'
Can you help me to learn more?
(Other definitions for trimaran that I've seen before include "Three-hulled vessel" , "type of boat" , "Three-hulled yacht" , "Sailing boat with three hulls" , "Three-hulled boat" .)