Judge having gas: is it shop talk? (6)
I believe the answer is:
jargon
'shop talk?' is the definition.
(I've seen this in another clue)
'judge having gas' is the wordplay.
'judge' becomes 'j' (abbreviation for judge).
'having' is a charade indicator (letters next to each other).
'gas' becomes 'argon' (argon is a gas).
'j'+'argon'='JARGON'
'is it' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for jargon that I've seen before include "Cant" , "Technical language" , "Argot" , "Insider idiom" , "Technical vocabulary" .)