The term 'Fit for Service' is a phrase used to describe an item or machine that is in good working condition and ready to be used. The crossword solutions for this term are 'Operable' (8 letters), 'Usable' (6 letters) and 'Onea' (4 letters). Operable means capable of being operated or used, Usable means capable of being used, and Onea means a unit of equipment that is in good working order. Together, these three words indicate that the item or machine is in good condition and ready to be used.