What does the cryptic crossword clue "One quits in clean fashion, which is futile (15)" mean?

The wordplay uses an anagram. anagram of ONE + QUITS + IN + CLEAN = INCONSEQUENTIAL The answer is INCONSEQUENTIAL.

One quits in clean fashion, which is futile (15)

Guardian Cryptic #25908 | 2 Down | 2013-03-29 flower