Bound to get on diving platform (11)
I believe the answer is:
springboard
'diving platform' is the definition.
(board for diving from)
'bound to get on' is the wordplay.
'bound' becomes 'spring' (both can mean to leap).
'to get on' becomes 'board' (eg boarding a train).
'spring'+'board'='SPRINGBOARD'
(Other definitions for springboard that I've seen before include "From which ideas may be launched" , "launch pad for ideas" , "something to give you a boost" , "Something to provide impetus" , "Gymnasts use it" .)