Is it difficult for our immune system to clear high risk hpv viruses if they enter our body?

Maybe/not. Most with a normal immune system will clear the primary infection and no longer spread it to others within 2 years. Those with weak immune systems may not. However, HPV strains have the ability to hibernate (while suppressed) and trigger cancerous changes years or decades later. The idea of "clearance" just applies to the contagious phase. Once you have HPV it can remain forever.