Framework of invention found in back of the box (8)
I believe the answer is:
espalier
'framework' is the definition.
(espalier is a kind of framework)
'invention found in back of the box' is the wordplay.
'invention' becomes 'lie'.
'found in' indicates putting letters inside.
'back of' says to take the final letters.
'box' becomes 'spar' (sparring is a kind of boxing).
The final letter of 'the' is 'e'.
'e'+'spar'='espar'
'lie' going inside 'espar' is 'ESPALIER'.
'of' acts as a link.
(Other definitions for espalier that I've seen before include "Lattice-work for training trees" , "Trellis on which shrubs are trained, like pearlies" , "fruit tree forced flat" , "Lattice for growing plants" , "flattened tree" .)