Military leader's fallen off potty (4)

I believe the answer is:

army

I'm a little stuck... Click here to teach me more about this clue!

'military' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for army that I've seen before include "Fighting force" , "Throng" , "A great number (of soldiers?)" , "Horde" , "Collective term for caterpillars" .)

I've seen this clue in The Telegraph.

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