What does the cryptic crossword clue "Blunder with running shoe type (4-2)" mean?

The wordplay uses a charade (building blocks). SLIP (synonym="‘blunder’") + ON (synonym="‘running’") = SLIPON The answer is SLIPON.

Blunder with running shoe type (4-2)

Guardian Cryptic #29445 | 27 Across | 2024-07-26 flower