This is a charade - two separate parts are joined together to form the answer word.
Break this into two parts: first, figure out what 'A couple short of a dozen' gives you as a number. Second, 'legs' in cricket terminology refers to a specific side - what abbreviation represents this side?
Answer: TENONS | TEN (a couple short of a dozen - two less than twelve) + ONS (legs in cricket, meaning the 'on' side, which is the leg side)