Turn on United supporter as it happens (8)

I believe the answer is:

actually

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'as it happens' is the definition.

'turn on united supporter' is the wordplay.
'turn on' becomes 'act' (theatre. I am not sure about the 'on' bit.**).
'united' becomes 'u'.
'supporter' becomes 'ally' (I've seen this before).
'act'+'u'+'ally'='ACTUALLY'

Can you help me to learn more?

(Other definitions for actually that I've seen before include "As a matter of fact" , "Really existing" , "In reality" , "A lay cult may be existing in fact" , "Really, in fact" .)

I've seen this clue in The Telegraph.

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