Single idea lost in translation (8)
I believe the answer is:
isolated
'single' is the definition.
(thesaurus)
'idea lost in translation' is the wordplay.
'in translation' is an anagram indicator (I've seen this in other clues).
'idea'+'lost'='idealost'
'idealost' is an anagram of 'ISOLATED'.
(Other definitions for isolated that I've seen before include "Solitary" , "hard to find" , "Segregated" , "Set apart, quarantined" , "Single" .)