Definitions of entry clearance
an official document that allows a person to enter a country for a specific purpose
If you intend to travel to the UK for a holiday for up to six months, you do not need to gain Entry Clearance in this capacity.
official permission for a person to enter a country for a specific purpose
The Home Office has introduced Biometric Residence Permits for applicants applying for entry clearance to come to the UK for more than six months.