Severe reprimand for firework (6)
I believe the answer is:
rocket
I believe this is a double definition.
'severe reprimand' is the first definition.
(I've seen this before)
'firework' is the second definition.
(rocket is a kind of firework)
'for' is the link.
(Other definitions for rocket that I've seen before include "Structure that flies by expelling gases - or a reprimand" , "Soar" , "Severe reprimand" , "Firework - sharp lecture" , "It's propelled to a great height by combustion" .)