Single idea lost in translation (8)
I believe the answer is:
Here is my best explanation:
'single' is the definition.
'idea lost in translation' is the wordplay.
'in translation' is an anagram indicator (I've seen this in other clues).
'idealost' is an anagram of 'ISOLATED'.
(Other definitions for isolated that I've seen before include "Off the beaten track", "Set apart, quarantined", "Cut off, remote", "Without accompaniment", "kept separate", "Solitary", "(Left) on one's own", "hard to find", "placed apart" and "Remote, set apart".)