The term 'MOST SPARE' can be defined by three crossword solutions: MEREST (6 letters), LEANEST (7 letters), and REEDIEST (8 letters). MEREST means having the least amount or fewest of something, LEANEST means having the least amount of fat or excess, and REEDIEST means having the least amount of solid material. Therefore, the term 'MOST SPARE' can be interpreted as having the least amount of something, the least amount of fat or excess, and the least amount of solid material.