What does the cryptic crossword clue "Retreat (wow) turned out to be elevated structure (5,5)" mean?

The wordplay uses an anagram. anagram of RETREAT + (WOW) = WATERTOWER The answer is WATERTOWER.

Retreat (wow) turned out to be elevated structure (5,5)

Daily Mail Cryptic #16999 | 13 Across | 2022-12-28 flower