What does the cryptic crossword clue "Number of clean sheets taking up most of line (3)" mean?

The definition is "line". The wordplay uses a reversal. LIN (reversal="LIN") = NIL; definition: "Number of clean sheets" The answer is NIL.

Number of clean sheets taking up most of line (3)

Independent Cryptic #11742 | 24 Down | 2024-05-29 flower