King on Hampshire river where trout prepared? (7)
I believe the answer is:
kitchen
'where trout prepared?' is the definition.
(trout might be prepared in a kitchen)
'king on hampshire river' is the wordplay.
'king' becomes 'K' (abbreviation for king in chess).
'on' means one lot of letters go next to another.
'hampshire river' becomes 'Itchen' (River Itchen in Hampshire).
'k'+'itchen'='KITCHEN'
(Other definitions for kitchen that I've seen before include "Galley" , "food prepared here" , "Room with cooking facilities" , "Place to prepare food" , "In workplace" .)