Crossword Genius

A hot-tempered expression (4)

Ross

I believe the answer is:

oath

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'expression' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?

'a hot-tempered' is the wordplay.
'tempered' indicates an anagram (temper can mean to adjust or modify).
'a'+'hot'='ahot'
'ahot' with letters rearranged gives 'OATH'.

Can you help me to learn more?

(Other definitions for oath that I've seen before include "Curse or solemn word" , "Curse - sworn statement" , "Tedious task" , "It's taken in court" , "A curse or a vow" .)

I've seen this clue in The Globe and Mail.
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