Success splitting rotating barrel to make a washing machine (4-3)
I believe the answer is:
twin-tub
'a washing machine' is the definition.
(I've seen this before)
'success splitting rotating barrel' is the subsidiary indication.
'success' becomes 'win'.
'splitting' indicates putting letters inside.
'rotating' shows that the letters should be reversed in order.
'barrel' becomes 'butt' (butt is a kind of barrel**).
'butt' in reverse letter order is 'ttub'.
'win' going within 'ttub' is 'twintub'.
'to make' is the link.
(Other definitions for twin-tub that I've seen before include "Dual washing-machine" , "Type of washing machine" , "Washing machine with two revolving drums" .)