In clinical industry, there is not much face-to-face interaction with people as mostly people are working remotely from home. So, there is not much fancy dressing and people do not require wearing suits. People can wear causal clothes.
Being an employee in a CRO, you can wear dress pants with a leather belt which makes it a bit classical. A pair of leather shoes with dress pants that are matching with your belt looks better than causal dressing and you look more like a gentleman. Check shirt which can either be polo or button down collared shirt but button down collared shirts are less casual and people most commonly wear these shirts. You can also wear a tie which is not necessary but wearing a tie looks fancier. Wearing a tie makes you look more presentable and people mostly wear ties when they are having a presentation and in winters you can also wear a jacket or a coat.
Polo collared shirts looks more cool and are more comfortable especially when going for a break from job.
People working remotely from home can wear anything because they don’t require going out of their house and they can work on their laptops after getting up from their beds. So they can even wear pajamas.