What does the cryptic crossword clue "Encircled by him, men seized monster (7)" mean?

The definition is "monster". The wordplay uses a hidden word. Hidden in "encircled by hIM, MEN SEized monster" The answer is Immense.

Encircled by him, men seized monster (7)

Telegraph Prize Cryptic #3086 | 14 Across | 2020-12-13 flower