What does the cryptic crossword clue "One Goth when mobilised is very active (2,3,2)" mean?

The definition is "very active". The wordplay uses an anagram. anagram of ONE + GOTH = ONTHEGO; definition: "very active" The answer is ONTHEGO.

One Goth when mobilised is very active (2,3,2)

Daily Mail Cryptic #17080 | 27 Across | 2023-04-20 flower