English law set up after weapon used in part of boat (7)
I believe the answer is:
gunwale
'part of boat' is the definition.
(the upper edge of the hull of a boat)
'english law set up after weapon' is the wordplay.
'english' becomes 'E' (abbreviation).
'set up' says the letters should be written in reverse.
'after' is a charade indicator (letters next to each other).
'weapon' becomes 'gun' (gun is a kind of weapon).
'e'+'law'='elaw'
'elaw' reversed gives 'wale'.
'wale' put after 'gun' is 'GUNWALE'.
'used in' is the link.
(Other definitions for gunwale that I've seen before include "Topmost planking of a wooden vessel's hull" , "Topmost planking of a wooden vessel" , "Part of craft" , "board" , "part of boat" .)