The most common and most likely answer to this crossword clue is the 9 letter word IDIOMATIC
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More clues leading to the result IDIOMATIC
- Close relative’s crazy about conforming to established usage
- Foolish keeping mum, in a manner of speaking
- Graduate in absurd situation using language like a native
- MoD cat has three eyes with an ear – freakish characteristic
- Foolish to cling to degree of particularity in language
- It would be stupid if mother leaves, in a manner of speaking
- Stupid to keep mum regarding one variety of language
- Using common language, mum punches halfwit in charge
- Barking welcomes parent using dialect
- The old woman filling potty, in a manner of speaking
Buddy explains!

The straight part
We know that "Using common language" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case using common language = idiomatic.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 IDIOMATIC mean?
IDIOMATIC noun- A manner of speaking, a mode of expression peculiar to a language, person, or group of people.
- A language or language variety; specifically, a restricted dialect used in a given historical period, context etc.
- An established expression whose meaning is not deducible from the literal meanings of its component words, often peculiar to a given language.
- An artistic style (for example, in art, architecture, or music); an instance of such a style.
- A programming construct or phraseology that is characteristic of the language.
- Pertaining or conforming to the natural mode of expression of a language.
- Containing or using many idioms.
- Resembling or characteristic of an idiom.
- Parts or pieces which are written both within the natural physical limitations of the instrument and human body and, less so or less often, the styles of playing used on specific instruments.