Mental ability of supporter with overall control (10)
I believe the answer is:
brainpower
'mental ability' is the definition.
'brainpower' can be an answer for 'ability' (brainpower is a kind of ability). I'm not certain of the 'mental' bit.
'supporter with overall control' is the wordplay.
'supporter' becomes 'bra' (a bra gives support to breasts).
'with overall control' becomes 'inpower' (I am not sure about this - if you are sure you should believe this answer much more).
'bra'+'inpower'='BRAINPOWER'
'of' is the link.
Can you help me to learn more?
(Another definition for brainpower that I've seen is " intelligence".)