Gas produced by an organ (5)
I believe the answer is:
argon
'gas' is the definition.
(argon is a gas)
'by an organ' is the wordplay.
'organ' can be anagrammed to 'ARGON'.
Though, I'm unsure how the anagram is indicated.
'produced' acts as a link.
Can you help me to learn more?
(Other definitions for argon that I've seen before include "noble element" , "Inert gas in atmosphere" , "Organ (anag.)" , "Inert gas, symbol Ar" , "rare gas" .)