Platform for a lad -- punch thrown (6,3)
I believe the answer is:
launch pad
'platform' is the definition.
(launch pad is a kind of platform)
'a lad punch thrown' is the wordplay.
'thrown' indicates an anagram.
'a'+'lad'+'punch'='aladpunch'
'aladpunch' with letters rearranged gives 'LAUNCH PAD'.
'for' acts as a link.
(Other definitions for launch pad that I've seen before include "that can kick-start career" , "Where to use rocket" , "Rocket's starting point" , "platform" , "Structure on which a rocket sits" .)