Bitter and excellent case of beer on the counter (5)
I believe the answer is:
'bitter' is the definition.
'excellent case of beer on the counter' is the wordplay.
'excellent' becomes 'ace' (I've seen this before).
'case of' says to hollow out the word (remove centre letters) (outsides of).
'on the counter' says the letters should be written in reverse (counter can mean in the opposite direction).
'beer' with its middle removed is 'br'.
'br' backwards is 'rb'.
'and' is the link.
(Other definitions for acerb that I've seen before include "Sour, bitter", "harsh and bitter", "tart", "sharp".)