Short measure (4)
I believe this clue is a double definition.
'short' is the first definition.
(both can mean a small alcoholic drink)
'measure' is the second definition.
(dram is a kind of measure)
(Other definitions for dram that I've seen before include "Measure of spirits" , "slug" , "Small drink of alcohol" , "Wee drop of whisky?" , "Measure of Scotch" .)
'short measure' is the definition.
'mil' can be an answer for 'measure' (thesaurus). I am not sure about the 'short' bit.
'short measure' is the wordplay.
'short' means to remove the last letter.
'measure' becomes 'mile' (measure of distance).
'mile' with its last letter taken away is 'MIL'.
Can you help me to learn more?
(Other definitions for mil that I've seen before include "One / one thousand inch" , "tiny distance" , "One thousanth of an inch" , "One thousandth of an inch" .)