The most common and most likely answer to this crossword clue is the 6 letter word PUDDLE
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More clues leading to the result PUDDLE
Buddy explains!

The straight part
We know that "the/pool" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the/pool = puddle.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 PUDDLE mean?
PUDDLE noun- A small pool of water, usually on a path or road.
- Stagnant or polluted water.
- A homogeneous mixture of clay, water, and sometimes grit, used to line a canal or pond to make it watertight.
- The ripple left by the withdrawal of an oar from the water.
- To form a puddle.
- To play or splash in a puddle.
- Of butterflies, to congregate on a puddle or moist substance to pick up nutrients.
- To process iron, gold, etc., by means of puddling.
- To line a canal with puddle (clay).
- To collect ideas, especially abstract concepts, into rough subtopics or categories, as in study, research or conversation.
- To make (clay, loam, etc.) dense or close, by working it when wet, so as to render impervious to water.
- To make foul or muddy; to pollute with dirt; to mix dirt with (water).