The most common and most likely answer to this crossword clue is the 4 letter word MALT
I've seen this crossword clue in The Guardian
M
A
L
T
More clues leading to the result MALT
- Island nation bans a whisky
- Graduate and lieutenant making whisky
- Whisky and mead oddly left at the end of banquet
- Rodent circling key hotel where brewer keeps grain
- Spirit needed by animal trainer
- Island nation cut liquor
- Spirit abuse needs to be cut by half
- My agile, lean thoughtful leadership could be moonshine
- Minute example of key drink
- Whisky misuse is reduced by half
Buddy explains!

The straight part
We know that "could be moonshine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case could be moonshine = malt.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 MALT mean?
MALT noun- Malted grain (sprouted grain) (usually barley), used in brewing and otherwise.
- Malt liquor, especially malt whisky.
- A milkshake with malted milk powder added for flavor.
- Maltose-rich sugar derived from malted grain.
- To convert a cereal grain into malt by causing it to sprout (by soaking in water) and then halting germination (by drying with hot air) in order to develop enzymes that can break down starches and proteins in the grain.
- To become malt.
- To drink malt liquor.