What does the cryptic crossword clue "This could make blind sump freer (8,6)" mean?

The wordplay uses an anagram. anagram of BLIND + SUMP + FREER = PLUMBERSFRIEND The answer is PLUMBERSFRIEND.

This could make blind sump freer (8,6)

Daily Mail Cryptic #16638 | 26 Across | 2021-08-10 flower