Graduate invested in funds for African fortress (6)
I believe the answer is:
casbah
'african fortress' is the definition.
(type of North African fortress)
'graduate invested in funds' is the wordplay.
'graduate' becomes 'BA' (someone with a Bachelor of Arts degree).
'invested in' indicates putting letters inside.
'funds' becomes 'cash' (I've seen this before).
'ba' placed within 'cash' is 'CASBAH'.
'for' is the link.
(Other definitions for casbah that I've seen before include "area of Marrakech?" , "From Arab area" , "area round Algiers fortress" , "North African citadel" , "Area around a castle in Algiers" .)