What does the cryptic crossword clue "Foul reek — old and new sewers produce it (10)" mean?

The wordplay uses an anagram. anagram of REEK OLD NEW = NEEDLEWORK The answer is NEEDLEWORK.

Foul reek — old and new sewers produce it (10)

Guardian Cryptic #25714 | 15 Across | 2012-08-14 flower