What does the cryptic crossword clue "Restraint for revolting reds arrested by police (8)" mean?

The wordplay uses an anagram. anagram of REDS (synonym="REDS") + HEAT (synonym="slang for the police") = HEADREST The answer is HEADREST.

Restraint for revolting reds arrested by police (8)

Guardian Cryptic #29582 | 8 Down | 2025-01-03 flower