Pair, however, returned washing machine (4-3)
I believe the answer is:
twin-tub
'washing machine' is the definition.
(I've seen this before)
'pair however returned' is the subsidiary indication.
'pair' becomes 'twin' ('twin' can be a synonym of 'pair'**).
'however' becomes 'but' (I've seen this before).
'returned' says the letters should be written in reverse.
'but' reversed gives 'tub'.
'twin'+'tub'='twintub'
(Other definitions for twin-tub that I've seen before include "Dual washing-machine" , "Type of washing machine" , "Washing machine with two revolving drums" .)