Tough little pieces skinned (4)
I believe the answer is:
hard
'tough' is the definition.
(I know that tough can be written as hard)
'little pieces skinned' is the wordplay.
'little pieces' becomes 'shards' (eg shards of glass).
'skinned' indicates the central letters.
The central letters of 'shards' are 'HARD'.
(Other definitions for hard that I've seen before include "Solid; tough" , "Difficult; severe" , "Tough - difficult" , "Emergency lane" , "badly" .)