Make box to contain energy (6)
I believe the answer is:
create
'make' is the definition.
(I know that make can be written as create)
'box to contain energy' is the wordplay.
I cannot quite understand how this works, but
'energy' could be 'e' (physics symbol as in E=mc2) and 'e' is found in the answer.
'box' could be 'crate' (crate is a kind of box) and 'crate' is found within the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for create that I've seen before include "Make, Porduce" , "Design" , "make a scene" , "Concoct" , "coin" .)