What does the cryptic crossword clue "Mushroom in group coming up (6)" mean?

The wordplay uses a reversal. IN (synonym="IN") + KCAP (synonym="PACK=group; “coming up” indicates vertical reversal") = INKCAP The answer is INKCAP.

Mushroom in group coming up (6)

Independent Cryptic #11864 | 5 Down | 2024-10-18 flower