He questionably claims penny on being given cash (9)
I believe the answer is:
pretender
'he questionably claims' is the definition.
(someone with a questionable claim to the throne)
'penny on being given cash' is the wordplay.
'penny' becomes 'p' (short for pence).
'on' becomes 're' ('on' can be mean 'with reference to').
'being given cash' becomes 'tender' (I am not sure about this - if you are sure you should believe this answer much more).
'p'+'re'+'tender'='PRETENDER'
Can you help me to learn more?
(Other definitions for pretender that I've seen before include "One acting" , "One claiming a title" , "Claimant, like Bonnie Prince Charlie" , "Claimant to a throne, usually without just title" , "One who claims a title or position" .)