The term 'Fit for Duty' is a phrase used to describe an individual who is ABLE to perform the duties of a job. The two crossword solutions, 'ABLE' and 'ONEA', are both four letter words that can be used to describe someone who is fit for duty. 'ABLE' is an adjective meaning having the power, skill, or resources to do something, while 'ONEA' is an acronym for 'Occupational Noise Exposure Assessment', which is a type of assessment used to determine if an individual is fit to work in a noisy environment.