The wife's language? (5)
I believe the answer is:
dutch
I believe this is a double definition.
'the wife's' is the first definition.
(slang term)
'language?' is the second definition.
(Dutch is an example)
(Other definitions for dutch that I've seen before include "From Amsterdam, perhaps" , "Netherlandish language" , "Relating to the Netherlands" , "European - wife" , "A European; pay-for-oneself (treat)" .)