Come on, it's difficult for financial expert (9)
I believe the answer is:
economist
'financial expert' is the definition.
(I've seen this before)
'come on it's difficult' is the wordplay.
'difficult' is an anagram indicator.
'come'+'on'+'its'='comeonits'
'comeonits' with letters rearranged gives 'ECONOMIST'.
'for' acts as a link.
(Other definitions for economist that I've seen before include "John Maynard Keynes for instance" , "Expert in all aspects of wealth" , "government adviser, possibly" , "Expert on finances" , "Expert in the management of a country's material resources" .)