What does the cryptic crossword clue "What's formed by tempest or monsoon? (5)" mean?

The definition is "What’s formed by tempest or monsoon / st or m". The wordplay uses a hidden word. hidden as above. The answer is STORM.

What's formed by tempest or monsoon? (5)

Times Cryptic #29175 | 21 Down | 2025-03-12 flower