What does the cryptic crossword clue "Being forced out of shell contributes to boy's terror (6)" mean?

The wordplay uses a hidden word. Hidden in bOYS TERror; an oyster is a “being” that is forced out of its shell to be eaten The answer is OYSTER.

Being forced out of shell contributes to boy's terror (6)

Guardian Cryptic #29210 | 22 Across | 2023-10-25 flower