What does the cryptic crossword clue "Untrustworthy partner abused trade rule (9)" mean?

The definition is "Untrustworthy partner". The wordplay uses an anagram. anagram of TRADE RULE = ADULTERER The answer is ADULTERER.

Untrustworthy partner abused trade rule (9)

Independent Cryptic #11927 | 10 Across | 2024-12-31 flower