The most common and most likely answer to this crossword clue is the 8 letter word FLAVOURS
I've seen this crossword clue in The Guardian
F
L
A
V
O
U
R
S
Buddy explains!
The straight part
We know that "Bitter and sour, say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bitter and sour, say = flavours.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does FLAVOURS mean?
FLAVOURS noun- The quality produced by the sensation of taste or, especially, of taste and smell in combined effect.
- A substance used to produce a taste. Flavoring.
- A variety (of taste) attributed to an object.
- The characteristic quality of something.
- A kind or type.
- One of the six types of quarks (top, bottom, strange, charmed, up, and down) or three types of leptons (electron, muon, and tauon).
- The quality produced by the sensation of smell; odour; fragrance.
- To add flavoring to something.