Achieve promotion in the outfit (5)

I believe the answer is:

getup

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'the outfit' is the definition.
('getup' can be a synonym of 'outfit')

'achieve promotion' is the wordplay.
'achieve' becomes 'get' (I've seen this in another clue).
'promotion' becomes 'up' (I can't justify this - if you can you should believe this answer much more).
'get'+'up'='GETUP'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for getup that I've seen before include "Study" , "clothes > stand" .)

I've seen this clue in the Evening Standard.

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