What does the cryptic crossword clue "Having been in a crash, I clam up in Civic (9)" mean?

The definition is "Civic". The wordplay uses an anagram. anagram of IN + I + CLAM + UP = MUNICIPAL; definition: "Civic" The answer is MUNICIPAL.

Having been in a crash, I clam up in Civic (9)

Independent Cryptic #12023 | 11 Across | 2025-04-22 flower