Cut the key a shade inaccurately (6)
I believe the answer is:
gashed
'cut' is the definition.
(synonyms)
'key a shade inaccurately' is the wordplay.
'key' becomes 'g' (musical key).
'inaccurately' is an anagram indicator.
'shade' anagrammed gives 'ashed'.
'g'+'ashed'='GASHED'
'the' is the link.
(Other definitions for gashed that I've seen before include "Cut open" , "Wounded" , "Deeply cut" .)