Genesis, Collins' opening helping to keep energy (8)
I believe the answer is:
creation
'genesis' is the definition.
(thesaurus)
'collins' opening helping to keep energy' is the wordplay.
'opening' says to take the initial letters.
'helping' becomes 'ration' (I've seen this before).
'to keep' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
The initial letter of 'collins' is 'c'.
'ration' enclosing 'e' is 'reation'.
'c'+'reation'='CREATION'
(Other definitions for creation that I've seen before include "work" , "Establishment" , "Something that has been made" , "The bringing into existence of something" , "The making of something out of nothing" .)