Distance of less than a mile (3)
I believe the answer is:
mil
'distance' is the definition.
(I have seen 'tiny distance' mean 'mil' so perhaps 'distance' could also mean 'mil')
'less than a mile' is the wordplay.
'less than' means to remove the last letter (not the full word).
'mile' with its final letter taken away is 'MIL'.
'of' is the link.
(Other definitions for mil that I've seen before include "tiny distance" , "One thousanth of an inch" , "One thousandth of an inch" , "One / one thousand inch" .)