A soldierly measure? (3)
I believe the answer is:
mil
'measure?' is the definition.
(mil is a kind of measure)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for mil that I've seen before include "One thousandth of an inch" , "One thousanth of an inch" , "One / one thousand inch" , "tiny distance" .)