Bent over London wife's nonsense (6,5)
I believe the answer is:
double dutch
'nonsense' is the definition.
(double Dutch is a kind of nonsense)
'bent over london wife's' is the wordplay.
'bent over' becomes 'double' (as in being doubled over).
'london wife' becomes 'dutch' (Cockney term for a wife).
'double'+'dutch'='DOUBLE-DUTCH'
(Other definitions for double dutch that I've seen before include "Nonsense (involving two wives?)" , "Nonsensical" , "Incomprehensible language" , "result of bigamy?" , "Gibberish (from both Amsterdam and Rotterdam?)" .)