It keeps some afloat above deserted platform (9)
I believe the answer is:
overdraft
'it keeps some afloat' is the definition.
The definition suggests a singular noun which matches the answer.
'above deserted platform' is the wordplay.
'above' becomes 'over' (I've seen this before).
'deserted' becomes 'd'.
'platform' becomes 'raft' (I have seen 'Buoyant platform' mean 'raft' so perhaps 'platform' could also mean 'raft').
'over'+'d'+'raft'='OVERDRAFT'
Can you help me to learn more?
(Other definitions for overdraft that I've seen before include "Potential problem with bank" , "Bank facility to go into the red" , "financial licence" , "shows lack of balance" , "Bank facility to spend more than you have" .)