What does the cryptic crossword clue "Nitre swirling around - it's a problem for the eyes (9)" mean?

The wordplay uses an anagram. anagram of NITRE (synonym="NITRE") + IT (synonym="IT") + IS (synonym="IS") = RETINITIS The answer is RETINITIS.

Nitre swirling around - it's a problem for the eyes (9)

Independent Cryptic #11956 | 18 Across | 2025-02-03 flower