Criminal one lynched, keeping isolated (6)
I believe the answer is:
lonely
'isolated' is the definition.
(thesaurus)
'criminal one lynched keeping' is the wordplay.
'keeping' indicates a hidden word.
'LONELY' is hidden within 'criminal one lynched'.
(Other definitions for lonely that I've seen before include "Without companionship" , "Isolated" , "... in need of company ..." , "Forlorn, solitary" , "Without companions" .)