What does the cryptic crossword clue "Christening baby after rear wiped, bun on it combed back first (9)" mean?

The wordplay uses a charade (building blocks). BAP (synonym=""bun"") + IT (reversal="IT") + SMAL (synonym="l") = BAPTISMAL The answer is BAPTISMAL.

Christening baby after rear wiped, bun on it combed back first (9)

Guardian Cryptic #29455 | 21 Across | 2024-08-07 flower