Provide financial investment here again (4)
I believe the answer is:
back
'here again' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for back that I've seen before include "Series of popular time-travel movies" , "Support - rear" , "Golf holes 10-18" , "Support; in return" , "Place where secret deals are done" .)