Least distant (7)
I believe the answer is:
nearest
'least distant' is the definition.
('near' is the opposite of 'distant' so 'nearest' should be a synonym for 'least distant')
This is the entire clue.
(Other definitions for nearest that I've seen before include "Next" , "With dearest, they're our loved ones" , "Most intimate" , "Closest among relatives" , "Rat seen (anag.)" .)