Boxer’s pleasure boat (7)
I believe the answer is:
cruiser
This clue is a double definition.
'boxer's' is the first definition.
(cruiser-weight is a type of boxer)
'pleasure boat' is the second definition.
('cruiser' can be a synonym of 'pleasure boat')
(Other definitions for cruiser that I've seen before include "Large warship" , "Relatively fast warship" , "Ship" , "Old warship" , "Type of warship" .)