Language and impertinence encapsulates fashionable type of humour (6-2-5)

I believe the answer is:
tongue-in-cheek
'language and impertinence encapsulates fashionable type of humour' is the definition.
I can't tell whether this defines the answer.
'language and impertinence encapsulates fashionable type of' is the wordplay.
'language' becomes 'tongue' (tongue can mean a language).
'and' means one lot of letters go next to another.
'impertinence' becomes 'cheek' (synonyms).
'encapsulates' indicates putting letters inside.
'fashionable type of' becomes 'in' (I am not sure about this - if you are sure you should believe this answer much more).
'tongue'+'cheek'='tonguecheek'
'tonguecheek' placed around 'in' is 'TONGUE-IN-CHEEK'.
Can you help me to learn more?
(Other definitions for tongue-in-cheek that I've seen before include "Ironically insincere" , "With ironic intention" , "Not seriously" , "With ironical intent" , "Light-hearted" .)
