Portions out investment (6)
I believe the answer is:
shares
'portions out' is the definition.
('share' can be a synonym of 'portion out')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for shares that I've seen before include "Distributes, gives portions to others" , "Carves up" , "Possesses or uses jointly with others, say a flat" , "Portions divided among a number" , "Divides out, allots" .)