What does the cryptic crossword clue "Length once more uncompleted in part of pool (4)" mean?

The wordplay uses a charade (building blocks). L (synonym="L") + ANE (synonym="ANE") = LANE The answer is LANE.

Length once more uncompleted in part of pool (4)

Guardian Cryptic #29672 | 24 Across | 2025-04-18 flower