Bitter, getting a key free (5)
I believe the answer is:
acrid
'bitter' is the definition.
(I know that bitter can be written as acrid)
'a key free' is the wordplay.
'key' becomes 'c' (musical key).
'free' becomes 'rid' (to be free of something is to be rid of it).
'a'+'c'+'rid'='ACRID'
'getting' is the link.
(Other definitions for acrid that I've seen before include "Greek goddess" , "Sharp - biting" , "irritating" , "Having a bitter smell or taste" , "causing corrosion" .)