What does the cryptic crossword clue "Unconventional ménage – or pair in this? (4,8)" mean?

The wordplay uses an anagram. anagram of MENAGEORPAIR ("menage - or pair") [anagram: "Unconventional"] = OPENMARRIAGE The answer is OPENMARRIAGE.

Unconventional ménage – or pair in this? (4,8)

Guardian Cryptic #29205 | 17 Across | 2023-10-19 flower