Upset at fiend showing teeth? (7)

I believe the answer is:

defiant

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

'upset at fiend showing teeth?' is the definition.
I can't tell whether this definition defines the answer.

'upset at fiend' is the wordplay.
'upset' indicates an anagram.
'at'+'fiend'='atfiend'
'atfiend' is an anagram of 'DEFIANT'.

Can you help me to learn more?

(Other definitions for defiant that I've seen before include "showing teeth!" , "Insubordinate" , "Mutinous" , "Uncooperative" , "Boldly resisting" .)

I've seen this clue in The Sun.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.