What does the cryptic crossword clue "What’s in this shoe? I don’t believe it! (2,4)" mean?

The definition is "What’s in this shoe? I don’t believe it!". The wordplay uses a double definition. Double definition The answer is MYFOOT.

What’s in this shoe? I don’t believe it! (2,4)

Guardian Cryptic #29674 | 9 Across | 2025-04-21 flower