What does the cryptic crossword clue "Bacon sandwiches upright on nipples (9)" mean?

The wordplay uses a container (one word inside another). PILLAR (synonym="upright") in PAY (synonym="Bacon") = PAPILLARY The answer is PAPILLARY.

Bacon sandwiches upright on nipples (9)

Guardian Cryptic #29576 | 24 Across | 2024-12-27 flower