What does the cryptic crossword clue "Set a boundary while a trend develops (4,3,4)" mean?

The wordplay uses an anagram. anagram of A + WHILE + TREND = DRAWTHELINE The answer is DRAWTHELINE.

Set a boundary while a trend develops (4,3,4)

Daily Mail Cryptic #17495 | 12 Across | 2024-11-22 flower