So far out - knowledge abandoned (8)
I believe the answer is:
forsaken
'abandoned?' is the definition.
('forsake' can be a synonym of 'abandon')
'so far out? knowledge' is the wordplay.
'out?' is an anagram indicator (out can mean wrong or inaccurate).
'knowledge' becomes 'ken' (ken is a kind of knowledge).
'so'+'far'='sofar'
'sofar' is an anagram of 'forsa'.
'forsa'+'ken'='FORSAKEN'
(Other definitions for forsaken that I've seen before include "Abandoned; renounced" , "Helpless" , "Left abandoned and deserted" .)