Go in for painting, etc., and language (5)
I believe the answer is:
argot
'language' is the definition.
(argot can mean jargon or slang)
'go in for painting etc' is the wordplay.
'in for' indicates putting letters inside.
'painting etc' becomes 'art' (painting is an art).
'go' going into 'art' is 'ARGOT'.
'and' acts as a link.
(Other definitions for argot that I've seen before include "Patois, vernacular" , "Jargon - patois" , "Language of a particular group" , "Groat (anag)" , "secret language" .)