Diagnose suffering (8)
I believe the answer is:
agonised
'suffering' is the definition.
('suffering'->'agonized' is in my internal thesaurus and 'ize'->'ise')
'diagnose' is the wordplay.
'diagnose' can be anagrammed to 'AGONISED'.
Though, I'm not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for agonised that I've seen before include "worried a lot" , "Tormented" , "suffered a lot" , "Struggled" , "Underwent mental anguish (over something)" .)