What does the cryptic crossword clue "Derestricted final agreement leads to collapse (10)" mean?

The wordplay uses a charade (building blocks). CONCERT (synonym="agreement") + INA (synonym="INA") = CONCERTINA The answer is CONCERTINA.

Derestricted final agreement leads to collapse (10)

Guardian Cryptic #29463 | 11 Across | 2024-08-16 flower