The most common and most likely answer to this crossword clue is the 9 letter word DYSPEPSIA
I've seen this crossword clue in Independent
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More clues leading to the result DYSPEPSIA
- Remedy sipped, say, for this?
- “It’s upsetting”, Pepys said, broken
- Spent days downing cola for wind problem
- Heartburn, said Pepys, should be treated
- Periods without a drink, a cause of internal discomfort
- Stomach problem could be brought by what’s sipped, say
- Days off consuming soft drink result in indigestion
- Days without a drink lead to agonising stomach complaint
- Days suffering without drink, having trouble with consumption
- “Upset stomach“, said Pepys in distress
Buddy explains!

The straight part
We know that "stomach complaint" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stomach complaint = dyspepsia.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 DYSPEPSIA mean?
DYSPEPSIA noun- Any mild disorder of digestion, characterised by stomach pain, discomfort, heartburn and nausea, often following a meal.