Sticking with host that's ready to fight (8,4)

I believe the answer is:

standing army

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

'ready to fight' is the definition.
I can't tell whether this defines the answer.

'sticking with host' is the wordplay.
'sticking with' becomes 'standing' (I can't justify this - if you can you should give a lot more credence to this answer).
'host' becomes 'army' (both can mean a large number of people).
'standing'+'army'='STANDING ARMY'

'that's' is the link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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