Tell agents I've upset preacher on box? (13)

I believe the answer is:

televangelist

'preacher on box?' is the definition.

'tell agents i've upset' is the wordplay.
'upset' indicates anagramming the letters.
'tell'+'agents'+'ive'='tellagentsive'
'tellagentsive' with letters rearranged gives 'TELEVANGELIST'.

(Other definitions for televangelist that I've seen before include "Revivalist who broadcasts" , "TV preacher" .)

I've seen this clue in The Telegraph.

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