The —, ITV talent show whose first winner was Steve Brookstein in 2004 (1,6)

I believe the answer is:

x factor

(Other definitions for x factor that I've seen before include "Magical 'something'" , "military hardship payment" , "Noteworthy special quality" , "'Hard to define but important special property (1,6)'" , "Noteworthy special talent" .)

I've seen this clue in The Mirror.

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