### Clue: Short distance initially measured in cubits reckoned outmoded nowadays (6)
### Answer: MICRON 
 ### Explanation: Definition: Short distance
  First letters,initially of Measured In Cubits Reckoned Outmoded Nowadays
Defn:  A millionth of a metre, but being replaced ("outmoded nowadays") by its proper name, the micrometre.  The ancient cubit, on the other hand, has long been outmoded; a word from the Latin for "elbow" and a length measured from the elbow to the tip of the middle finger (whose?)