In the highest position at work (4)

I believe the answer is:

atop

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'in the highest position' is the definition.
I can't tell whether this defines the answer.

'at work' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'at'+'op'='ATOP'

Can you help me to learn more?

(Other definitions for atop that I've seen before include "On the highest point" , "At the apex" , "Upon" , "In superior position" , "on the head" .)

I've seen this clue in the Evening Standard.

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