Identical edges of leaf found in seed (8)
I believe the answer is:
selfsame
'identical' is the definition.
('selfsame' can be a synonym of 'identical')
'edges of leaf found in seed' is the wordplay.
'edges of' means to remove the middle letters.
'found in' means one lot of letters goes inside another.
'seed' becomes 'sesame' (sesame seed is a kind of seed**).
'leaf' with its middle removed is 'lf'.
'lf' going into 'sesame' is 'SELFSAME'.
(Other definitions for selfsame that I've seen before include "Exactly identical" , "The identical kind, not changed or different" .)