Area 51 opens up belief in invisible controlling powers (8)
I believe the answer is:
religion
'up belief in invisible controlling powers' is the definition.
I can't tell whether this defines the answer.
'area 51 opens' is the wordplay.
'area' becomes 'region' (synonyms).
'51' becomes 'LI' (roman numeral).
'opens' means one lot of letters goes inside another (one set of letters makes an 'opening' in another).
'region' enclosing 'li' is 'RELIGION'.
Can you help me to learn more?
(Other definitions for religion that I've seen before include "System of divine worship" , "Institution to express belief in a god" , "System of belief or worship" , "Particular system of belief" , "Belief in and worship of god or gods" .)