Cash benefit in favour of the competent (6)
I believe the answer is:
profit
'cash benefit' is the definition.
'profit' can be an answer for 'benefit' (I've seen this before). I am not sure about the 'cash' bit.
'in favour of the competent' is the wordplay.
'in favour of' becomes 'pro' (being pro a particular cause).
'the competent' becomes 'fit' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pro'+'fit'='PROFIT'
Can you help me to learn more?
(Other definitions for profit that I've seen before include "Net gain after expenses" , "Gain from employment of capital" , "Financial gain" , "bonus" , "Advantage, benefit" .)