Philosophy old yogi developed around energy (8)
I believe the answer is:
ideology
'philosophy' is the definition.
(I know that ideology is a type of morality)
'old yogi developed around energy' is the wordplay.
'developed' is an anagram indicator.
'around' indicates putting letters inside.
'energy' becomes 'e' (physics symbol as in E=mc2).
'old'+'yogi'='oldyogi'
'oldyogi' with letters rearranged gives 'idology'.
'idology' going around 'e' is 'IDEOLOGY'.
(Other definitions for ideology that I've seen before include "Creed" , "Ideas that form the basis of a political theory" , "An ism" , "doctrine" , "Body of ideas" .)