The most common and most likely answer to this crossword clue is the 5 plus 4 letter word WATER BUTT
I've seen this crossword clue in Independent
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More clues leading to the result WATER BUTT
Buddy explains!
The straight part
We know that "it may be found at side of house" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it may be found at side of house = water butt.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 WATER BUTT mean?
WATER BUTT noun- An open-ended barrel used to contain rainwater; a rain barrel