What does the cryptic crossword clue "Samurai sword found in trunk at an armoury (6)" mean?

The definition is "Samurai sword". The wordplay uses a hidden word. Hidden in trunK AT AN Armoury The answer is KATANA.

Samurai sword found in trunk at an armoury (6)

Guardian Cryptic #29041 | 6 Across | 2023-04-11 flower