Had invested without credit (5)
I believe the answer is:
owned
'had' is the definition.
('own' can be a synonym of 'have')
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for owned that I've seen before include "Had possession of" , "Confessed" , "made a confession" , "admitted making confession" , "Possessed; admitted" .)