What does the cryptic crossword clue "Engulf wobbly bum in woollen fabric (8)" mean?

The wordplay uses an anagram. anagram of BUM (synonym="BUM") + SERGE (synonym="SERGE") = SUBMERGE The answer is SUBMERGE.

Engulf wobbly bum in woollen fabric (8)

Guardian Cryptic #29285 | 1 Down | 2024-01-22 flower