What does the cryptic crossword clue "Scottish tree one added to line (5)" mean?

The definition is "to line". The wordplay uses a charade (building blocks). ROW (synonym="line") + AN (synonym="one") = ROWAN The answer is ROWAN.

Scottish tree one added to line (5)

Independent Cryptic #11726 | 10 Across | 2024-05-10 flower