Bitter woman coming in to do a song (8)
I believe the answer is:
scathing
'bitter' is the definition.
(synonyms)
'woman coming in to do a song' is the wordplay.
I cannot quite see how this works, but
'woman' could be 'cathi' and 'cathi' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for scathing that I've seen before include "Severely critical" , "Harshly critical" , "Painful" , "Caustic" , "Acid" .)