An employer's clever device? (4)

I believe the answer is:

ploy

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

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

'an employer's clever' is the wordplay.
'PLOY' is hidden within the letters.
But, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for ploy that I've seen before include "Trick" , "Cunning plan" , "Clever tactic" , "Game manoeuvre" , "Device" .)

I've seen this clue in the Evening Standard.

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