Earth, say, where flower perhaps stores energy (6)
I believe the answer is:
planet
'earth say' is the definition.
(earth is a kind of planet)
'flower perhaps stores energy' is the wordplay.
'flower perhaps' becomes 'plant' (flower is a kind of plant).
'stores' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'plant' going around 'e' is 'PLANET'.
'where' is the link.
(Other definitions for planet that I've seen before include "Heavenly body moving round the sun" , "Neptune, for example" , "Celestial body that revolves around the sun" , "Large body orbiting sun" , "Jupiter is one" .)