Staff money expert (4)
I believe the answer is:
mace
'staff' is the definition.
(a mace is a ceremonial staff or stick)
'money expert' is the wordplay.
'money' becomes 'm' (abbreviation used in economics).
'expert' becomes 'ace' (ace can informally mean very good).
'm'+'ace'='MACE'
(Other definitions for mace that I've seen before include "something fragrant" , "Disabling spray" , "Spice; ceremonial baton" , "Ceremonial staff or kind of spice" , "One of 9 [CLUBS]" .)