Cooks with fashionable vessel (9)
I believe the answer is:
steamship
'vessel' is the definition.
(steamship is a kind of vessel)
'cooks with fashionable' is the wordplay.
'cooks' becomes 'steams' (steaming is a kind of cooking).
'with' means one lot of letters go next to another.
'fashionable' becomes 'hip' (hip can mean trendy or fashionable).
'steams'+'hip'='STEAMSHIP'
(Other definitions for steamship that I've seen before include "I pass them (anag) - vessel" , "SS in full" , "What SS stands for" , "Tramp, say" , "Queen Elizabeth, for one?" .)