Ultra dynamic jazz? (4)

I believe the answer is:

trad

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

'jazz?' is the definition.
(trad jazz is a type of jazz)

'ultra dynamic' is the wordplay.
'TRAD' is hidden in amongst the letters.
However, I am not sure how this is indicated.

Can you help me to learn more?

(Other definitions for trad that I've seen before include "Conventional (jazz)" , "Classical (abbr)" , "Style of jazz" , "Type of jazz or folk" , "(Of jazz) traditional" .)

I've seen this clue in the Evening Standard.

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