What does the cryptic crossword clue "A particular method to make such a mirror (3-3)" mean?

The wordplay uses a charade (building blocks). ONE (synonym="ONE") + WAY (synonym="”A particular method”") = ONEWAY The answer is ONEWAY.

A particular method to make such a mirror (3-3)

Guardian Cryptic #29399 | 29 Across | 2024-06-03 flower