Clever in getting mastermind to stay over (9)
I believe the answer is:
ingenious
'clever' is the definition.
(I know that clever can be written as ingenious)
'in getting mastermind to stay over' is the wordplay.
'getting mastermind' becomes 'genius' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to stay' indicates putting letters inside (stay can mean to restrain or control).
'over' becomes 'o' (cricket abbreviation).
'genius' enclosing 'o' is 'genious'.
'in'+'genious'='INGENIOUS'
Can you help me to learn more?
(Other definitions for ingenious that I've seen before include "Artless" , "Creative" , "Resourceful" , "Showing inventiveness" , "Displaying art" .)