Skipping regularly, Kirby exercises leg, producing gas (7)
I believe the answer is:
krypton
'gas' is the definition.
(I know that krypton is a type of argonon)
'skipping regularly kirby exercises leg' is the wordplay.
I cannot really see how this works, but
'exercises' could be 'pt' (Physical Training) and 'pt' is present in the answer.
'leg' could be 'on' (cricket term, fielding positions) and 'on' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'producing' acts as a link.
Can you help me to learn more?
(Other definitions for krypton that I've seen before include "Pry knot (anag) - gas" , "Gaseous element" , "Noble gas - Superman's birthplace" , "Superman's world and a gas" , "Chemical element, Kr" .)