What does the cryptic crossword clue "Sign given by head of militia abandoning tanks (8)" mean?

The definition is "Sign". The wordplay uses acrostic. AQUARIUS (deletion) = AQUARIUS; definition: "Sign" The answer is AQUARIUS.

Sign given by head of militia abandoning tanks (8)

Guardian Cryptic #29325 | 26 Across | 2024-03-08 flower