What does the cryptic crossword clue "Have disappeared after repeatedly extracting energy for gas (5)" mean?

The definition is "gas". The wordplay uses a deletion. AR (synonym="AR") + GON (synonym="GON") = ARGON; definition: "gas" The answer is ARGON.

Have disappeared after repeatedly extracting energy for gas (5)

Guardian Cryptic #29353 | 10 Across | 2024-04-10 flower