What does the cryptic crossword clue "Stuck out reminder about pastry’s filling (9)" mean?

The wordplay uses a container (one word inside another). TRUDE (synonym="TRUDE") in PROD (synonym="‘reminder’") = PROTRUDED The answer is PROTRUDED.

Stuck out reminder about pastry’s filling (9)

Guardian Cryptic #29640 | 15 Down | 2025-03-12 flower