Investing? Finish in debt! (8)
I believe the answer is:
endowing
'investing?' is the definition.
('endow' can be a synonym of 'invest')
'finish in debt' is the wordplay.
'finish' becomes 'end' ('end' can be a synonym of 'finish').
'in debt' becomes 'owing' (I've seen this before).
'end'+'owing'='ENDOWING'
(Other definitions for endowing that I've seen before include "Presenting" , "Making donations" .)