Informal (language) (10)
'informal language' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slang that I've seen before include "common language" , "manner of speaking" , "Unconventional language" , "See 15" , "Non-standard vocabulary" .)
'informal language' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for vernacular that I've seen before include "Native tongue - dialect" , "Characteristic language" , "Local-style" , "Native language" , "Everyday language" .)