Well-armed number challenged to depose king (9)

I believe the answer is:

tentacled

'well-armed' is the definition.
(having many tentacles)

I don't understand the rest of the clue.

(Other definitions for tentacled that I've seen before include "like squid" , "army?" , "Highly-armed" .)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app