What does the cryptic crossword clue "Like 8 27 in book fair, initially ignored (4)" mean?

The wordplay uses a charade (building blocks). B (synonym="book") + UST (synonym="fair") = BUST The answer is BUST.

Like 8 27 in book fair, initially ignored (4)

Guardian Cryptic #29571 | 26 Down | 2024-12-20 flower