Shine like firework, endlessly (7)
I believe the answer is:
sparkle
'shine' is the definition.
(I know that sparkle is a more specific form of the action shine)
'firework endlessly' is the wordplay.
'firework' becomes 'sparkler' (sparkler is a kind of firework).
'endlessly' means to remove the last letter.
'sparkler' with its final letter removed is 'SPARKLE'.
'like' acts as a link.
(Other definitions for sparkle that I've seen before include "Glittering light" , "Flash brightly" , "Gleam" , "Be vivacious and witty" , "dash" .)