What does the cryptic crossword clue "Secret police in almost unmoving position (5)" mean?

The definition is "Secret police". The wordplay uses a deletion. STASI (deletion) = STASI; definition: "Secret police" The answer is STASI.

Secret police in almost unmoving position (5)

Guardian Cryptic #29423 | 16 Across | 2024-07-01 flower