Identify the problem with English ballad getting to support all the characters in Revolution (8)

I believe the answer is:

diagnose

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'identify' is the definition.
(thesaurus)

I cannot understand how the rest of the clue works.

(Other definitions for diagnose that I've seen before include "Find cause of illness in San Diego" , "Agonised (anag.)" , "Determine the nature of a medical problem" , "Establish cause in San Diego" , "San Diego (anag)" .)

I've seen this clue in the Irish Times.

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