This is the 3763rd most frequent Russian word.
частных
"Private" or "individual" (genitive plural form).
Here, 'частных' is used as an adjective to describe 'клиник' (clinics), indicating that these clinics are privately owned or operated.
В городе есть много частных клиник.
There are many private clinics in the city.
In this sentence, 'частных' modifies 'проектах' (projects), indicating that these projects are privately funded or exclusive.
Она работает в частных проектах.
She works on private projects.
Here, 'частных' describes 'темах' (topics), showing that the topics are of a private or personal nature.