Crossword Genius

Prepare to strike when you promote one of the employees (5,1,4)

Ross

I believe the answer is:

raise a hand

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

'prepare to strike when you' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'promote one of the employees' is the wordplay.
I cannot quite see how this works, but
'promote' could be 'raise' (I've seen this before) and 'raise' is found in the answer.
'one' could be 'an' (an apple is one apple) and 'an' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Evening Standard.
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