Accomplished leader is devious (8)
I believe the answer is:
realised
'accomplished' is the definition.
('accomplished'->'realized' is in my internal thesaurus and 'ize'->'ise')
'leader is devious' is the wordplay.
'devious' is an anagram indicator.
'leader'+'is'='leaderis'
'leaderis' anagrammed gives 'REALISED'.
(Other definitions for realised that I've seen before include "Came to awareness" , "Became fully aware of or converted into money" , "Came to know" , "Came to understand" , "Came to be aware" .)