Call with the inside story; it may explain everything! (6,6)
I believe the answer is:
string theory
'it may explain everything' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'call with the inside story' is the wordplay.
'call' becomes 'ring' (telephone call).
'with' is a charade indicator (letters next to each other).
'inside' is an insertion indicator.
'ring'+'the'='ringthe'
'ringthe' inserted inside 'story' is 'STRING THEORY'.
Can you help me to learn more?
(Other definitions for string theory that I've seen before include "Idea relating to subatomic particles" , "Cosmological hypothesis concerning all fundamental particles - retrying tosh (anag)" , "One idea in particle physics" .)