Unexpectedly present a twisty firework (7)
I believe the answer is:
serpent
'a twisty firework' is the definition.
(firework with a twisting motion)
'unexpectedly present' is the wordplay.
'unexpectedly' indicates an anagram.
'present' is an anagram of 'SERPENT'.
(Other definitions for serpent that I've seen before include "Malicious person" , "(In literature) a snake" , "Present for a snake" , "Large snake; sly person" , "Venomous snake" .)