What does the cryptic crossword clue "Hero engages US comic in cause of global warming (10,3)" mean?

The wordplay uses an anagram. anagram of HERO + ENGAGES + US = GREENHOUSEGAS The answer is GREENHOUSEGAS.

Hero engages US comic in cause of global warming (10,3)

Daily Mail Cryptic #16399 | 15 Across | 2020-09-09 flower