What does the cryptic crossword clue "Obstruct progress? As well not perhaps (9)" mean?

The definition is "Obstruct". The wordplay uses an anagram. anagram of AS + WELL + NOT = STONEWALL; definition: "Obstruct" The answer is STONEWALL.

Obstruct progress? As well not perhaps (9)

Independent Cryptic #11909 | 14 Down | 2024-12-10 flower