Determined about reaching the top, property tycoon means to be heard (8,7)
I believe the answer is:
speaking trumpet
'means to be heard' is the definition.
(device for amplifying one's voice)
'determined about reaching the top property tycoon' is the wordplay.
'determined' becomes 'set' (similar in meaning).
'about' indicates putting letters inside.
'reaching the top' becomes 'peaking' (I can't explain this - if you can you should believe this answer much more).
'property tycoon' becomes 'Trump' (Donald Trump).
'peaking'+'trump'='peakingtrump'
'set' placed around 'peakingtrump' is 'SPEAKING-TRUMPET'.
Can you help me to learn more?
(Other definitions for speaking trumpet that I've seen before include "old loud-hailer" , "What may up deliveries" .)