Previously found in sheer edge (3)
I believe the answer is:
ere
'previously' is the definition.
('ere' can be a synonym of 'previously')
'in sheer edge' is the wordplay.
'in' indicates a hidden word.
'ERE' is hidden in the letters of 'sheer edge'.
'found' acts as a link.
(Other definitions for ere that I've seen before include "Before (in poetry)" , "Old prior" , "Archaic word for before - a palindrome" , "Old word for before" , "Before (literary)" .)