What does the cryptic crossword clue "This prevents experiments with Spooner’s ideal complexion (4,3)" mean?

The wordplay uses a charade (building blocks). TEST (synonym="TEST") + BAN (synonym="BAN") = TESTBAN The answer is TESTBAN.

This prevents experiments with Spooner’s ideal complexion (4,3)

Guardian Cryptic #29395 | 22 Across | 2024-05-29 flower