The most common and most likely answer to this crossword clue is the 6 letter word ALKALI
I've seen this crossword clue in Financial Times
A
L
K
A
L
I
More clues leading to the result ALKALI
- Talk a little covering chemical compound
- Those last seen in militia will attack Area 51 base
- Talk a little about a remedy for acid
- Boxer consumes cabbage endlessly, it neutralises acid
- Base crucial for walk, a lighthouse
- Goddess sits on aluminium base
- Hack’s latest article accepted by everyone on Independent – it’s basic stuff
- No time to talk with boxer in compound
- Antacid needed by boxer after talk starts late
- Walk a line, lacking directions for chemical base
Buddy explains!

The straight part
We know that "a remedy for acid" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a remedy for acid = alkali.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 ALKALI mean?
ALKALI noun- One of a class of caustic bases, such as soda, soda ash, caustic soda, potash, ammonia, and lithia, whose distinguishing peculiarities are solubility in alcohol and water, uniting with oils and fats to form soap, neutralizing and forming salts with acids, turning to brown several vegetable yellows, and changing reddened litmus to blue.
- (Western United States) Soluble mineral matter, other than common salt, contained in soils of natural waters.