I'm to referee next (9)

I believe the answer is:

immediate

'next' is the definition.
(thesaurus)

'i'm to referee' is the wordplay.
'to referee' becomes 'mediate' (I've seen this before).
'im'+'mediate'='IMMEDIATE'

(Other definitions for immediate that I've seen before include "Involving no delay" , "on the spot" , "Most urgent; current" , "Direct" , "Nearest" .)

I've seen this clue in The Telegraph.

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