Is uniform in effect for tonight? (4,7)

I believe the answer is:

this evening

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'for tonight?' is the definition.
('this evening' can be a synonym of 'tonight')

'is uniform in effect' is the wordplay.
'uniform' becomes 'even' (uniform can mean even or level).
'in' means one lot of letters goes inside another.
'effect' becomes 'thing' (I can't justify this - if you can you should believe this answer much more).
'is'+'even'='iseven'
'iseven' placed into 'thing' is 'THIS EVENING'.

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I've seen this clue in The Telegraph.

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