Pointless opening bitter (4)
I believe the answer is:
tart
This clue could be a double definition.
'pointless opening' is the first definition.
Both the answer and definition are adjectives. Maybe there's a link between them I don't understand?
'bitter' is the second definition.
(thesaurus)
Can you help me to learn more?
(Other definitions for tart that I've seen before include "Flat pie" , "Professional woman" , "Open cake with jam etc" , "Sarcastic" , "A bit sour like open cake" .)