Question put in vulgar language (6)
I believe the answer is:
basque
'language' is the definition.
(thesaurus)
'question put in vulgar' is the wordplay.
'question' becomes 'qu'.
'put in' means one lot of letters goes inside another.
'vulgar' becomes 'base' (I am not sure about this - if you are sure you should believe this answer much more).
'qu' put into 'base' is 'BASQUE'.
Can you help me to learn more?
(Other definitions for basque that I've seen before include "One lives in the Western Pyrenees on the Atlantic coast" , "underwear" , "People living in the Western Pyrenees in France and Spain" , "From a Spanish/French border region" , "Person from western Pyrenees" .)