The term 'Casualty of Casual Friday' refers to someone who has lost their job due to the implementation of a casual dress code on Fridays. The crossword solution for this term is 'NECKTIE', which is an item of clothing that is typically associated with formal attire. Neckties are often seen as a symbol of professionalism and are usually not worn in a casual setting. Therefore, the term 'Casualty of Casual Friday' can be used to describe someone who has lost their job due to the introduction of a more relaxed dress code on Fridays.