What does the cryptic crossword clue "Snack is crumbly but it is ace (10)" mean?

The definition is "Snack". The wordplay uses an anagram. anagram of BUT IT IS ACE = TEABISCUIT The answer is TEABISCUIT.

Snack is crumbly but it is ace (10)

Independent Cryptic #11845 | 13 Down | 2024-09-26 flower