Work that is done in the field is completed in a real natural environment rather than in a laboratory or office. Work done in the field is not carried out in a controlled way. Being in the field can also refer to being in a war or engaging in combat.

1. The new product works great in theory, but has yet to be tested in the field. A limited amount will be released to the public for a trial run next week.
2. Claire was by far the best candidate for the job. Not only is she well qualified, she also has a lot of experience in the field, with years of hands-on work under her belt.   

1. Karl is known for his work in the field of psychology and has been using his expertise in human behaviour to advise companies on how to identify the most suitable candidates for roles. 
2. I have been working in the field with patients for over 20 years so when I give advice I know what I'm talking about.