Somewhat badly restored old instrument (4)
I believe the answer is:
lyre
'old instrument' is the definition.
(I've seen this before)
'somewhat badly restored' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'LYRE' can be found hidden inside 'badly restored'.
(Other definitions for lyre that I've seen before include "Instrument played by Orpheus" , "Ancient Greek stringed instrument" , "Old stringed instrument" , "Harp used by ancient Greeks" , "Sort of harp" .)