The most common and most likely answer to this crossword clue is the 5 plus 3 letter word IDEAL GAS
I've seen this crossword clue in Independent
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More clues leading to the result IDEAL GAS
- Sage laid out an unrealistic scientific concept
- Hypothetical element in current trade talk
- . Island secures contract with Georgia for chemical quantity
- If everything’s perfect, theoretically, what could the matter be?
- Fish eating seaweed that’s chemically perfect?
- He perhaps, joins setter, to distribute perfectly behaving substance
- What a petrol bunk worker would say of a hypothetical fluid
Buddy explains!
The straight part
We know that "what could the matter be?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what could the matter be? = ideal gas.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.