Be valid as comedian (5-2)

I believe the answer is:

stand-up

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

'be valid' is the wordplay.
'be' becomes 'stand' (standing is a kind of being).
'valid' becomes 'up' (I can't justify this - if you can you should give a lot more credence to this answer).
'stand'+'up'='STAND-UP'

'as' acts as a link.

Can you help me to learn more?

(Other definitions for stand-up that I've seen before include "Performed solo (of a comedy routine)" , "Sort of comic (to be counted?)" , "Type of comedian" , "Form of comedy" .)

I've seen this clue in The Sun.

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