The most common and most likely answer to this crossword clue is the 3 letter word ICE
I
C
E
More clues leading to the result ICE
- Cooler that is cold inside
- Murder US-style, namely cold-hearted
- Something cold seen during Antarctic expedition
- Diamonds to decorate
- Rocks in circle, odd ones invisible
- Diamonds set evenly in circlet
- Reserve to move briskly, feeling the cold
- What Arctic explorer covers?
- Freeze ingredient for milk pudding that’s not started
- Slippery surface to kill American
Buddy explains!

The straight part
We know that "Cooler" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cooler = ice.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 ICE mean?
ICE noun- Water in frozen (solid) form.
- Any frozen volatile chemical, such as ammonia or carbon dioxide.
- Any volatile chemical, such as water, ammonia, or carbon dioxide, not necessarily in solid form.
- A frozen dessert made of fruit juice, water and sugar.
- An ice cream.
- Any substance having the appearance of ice.
- One or more diamonds and jewelry.
- Crystal form of amphetamine-based drugs.
- The area where a game of ice hockey is played.
- Money paid as a bribe.
- To cool with ice, as a beverage.
- To become ice; to freeze.
- To make icy; to freeze.
- To murder.
- To cover with icing (frosting made of sugar and milk or white of egg); to frost; as cakes, tarts, etc.
- To put out a team for a match.
- To shoot the puck the length of the playing surface, causing a stoppage in play called icing.