A hot bit of strong language (4)

I believe the answer is:

oath

I'm a little stuck... Click here to teach me more about this clue!

'strong language' is the definition.
(I've seen this before)

'a hot bit' is the wordplay.
'a hot' anagrams to 'OATH'.
But, I am not sure how the anagram is indicated.

'of' acts as a link.

Can you help me to learn more?

(Other definitions for oath that I've seen before include "in court, we take it" , "Swearword or solemn word" , "It could be ruddy when minced" , "Curse or solemn promise" , "darn, for example" .)

I've seen this clue in The Irish News.

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