Least far (7)
I believe the answer is:
nearest
'least far' is the definition.
('near' is the opposite of 'far' so 'nearest' should be a synonym for 'least far')
This is all the clue.
(Other definitions for nearest that I've seen before include "most like Scrooge at first" , "Stingiest" , "Closest, being earnest" , "Most closely related" , "Most adjacent" .)