The most common and most likely answer to this crossword clue is the 10 letter word UNICAMERAL
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More clues leading to the result UNICAMERAL
Buddy explains!

The straight part
We know that "having a single chamber" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case having a single chamber = unicameral.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 UNICAMERAL mean?
UNICAMERAL adjective- Of, or having, a single legislative chamber.
- Of a script or typeface: making no distinction between upper and lower case, but rather having only one case.