Noble element appears when listeners have left (5)
I believe the answer is:
argon
'noble element' is the definition.
(I've seen this before)
'when listeners have left' is the wordplay.
I cannot really understand how this works, but
'when' could be 'on' (I've seen this in other clues) and 'on' is found in the answer.
The remaining letters 'arg' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'appears' acts as a link.
Can you help me to learn more?
(Other definitions for argon that I've seen before include "noble element" , "Gas, 1% of atmosphere" , "Inert gas in atmosphere" , "Inert eighteen ac gas" , "Noble gas, Ar" .)