In favour of appropriate benefit (6)
I believe the answer is:
profit
'benefit' is the definition.
('profit' can be a synonym of 'benefit')
'in favour of appropriate' is the wordplay.
'in favour of' becomes 'pro' (I've seen this before).
'appropriate' becomes 'fit' ('fit' can be similar in meaning to 'appropriate').
'pro'+'fit'='PROFIT'
(Other definitions for profit that I've seen before include "It's gained on a transaction" , "Financial gain" , "Gain from employment of capital" , "bonus" , "Advantage, benefit" .)