Twin meeting wife gives incomprehensible speech (6,5)
I believe the answer is:
double dutch
'incomprehensible speech' is the definition.
(double Dutch can mean nonsensical talk)
'twin meeting wife' is the wordplay.
'twin' becomes 'double' (identical twins are each other's doubles).
'meeting' means one lot of letters go next to another.
'wife' becomes 'dutch' (slang term).
'double'+'dutch'='DOUBLE-DUTCH'
'gives' is the link.
(Other definitions for double dutch that I've seen before include "Gibberish (from both Amsterdam and Rotterdam?)" , "Incomprehensible language" , "Nonsense (involving two wives?)" , "taken on by bigamist?" , "result of bigamy?" .)