What does the cryptic crossword clue "Met ran riot, mistreated returning killer? (10)" mean?

The definition is "killer?". The wordplay uses an anagram. anagram of MET + RAN + RIOT, = TERMINATOR; definition: "killer?" The answer is TERMINATOR.

Met ran riot, mistreated returning killer? (10)

Guardian Cryptic #29562 | 2 Down | 2024-12-10 flower