What does the cryptic crossword clue "Plant (iris) adapts when neglected (10)" mean?

The definition is "Plant". The wordplay uses an anagram. anagram of (IRIS) + ADAPTS = ASPIDISTRA; definition: "Plant" The answer is ASPIDISTRA.

Plant (iris) adapts when neglected (10)

Guardian Cryptic #27910 | 16 Across | 2019-08-27 flower