Head start in rebuilding planet destroyer (5,4)
I believe the answer is:
death star
'planet destroyer' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'head start in rebuilding' is the wordplay.
'in rebuilding' indicates an anagram (I've seen this in other clues).
'head'+'start'='headstart'
'headstart' is an anagram of 'DEATH STAR'.
Can you help me to learn more?
(Another definition for death star that I've seen is " Empire's enormous battle station (Star Wars)".)