What does the cryptic crossword clue "Where queen would be executed — or hang, if theory is wrong (12)" mean?

The wordplay uses an anagram. anagram of HANG, + IF + THEORY = FOTHERINGHAY The answer is FOTHERINGHAY.

Where queen would be executed — or hang, if theory is wrong (12)

Times Cryptic #28818 | 20 Across | 2024-01-20 flower