Don't take a beating lying down? (5,2,4)

I believe the answer is:

stand to lose

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

'lying down?' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'don't take a beating' is the wordplay.
'don't' becomes 'standto' (I can't explain this - if you can you should believe this answer much more).
'take a beating' becomes 'lose' (I've seen this in another clue).
'standto'+'lose'='STAND TO LOSE'

Can you help me to learn more?

I've seen this clue in The Irish Independent.

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