Retiring investor? (6)
I believe the answer is:
backer
'investor?' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for backer that I've seen before include "Financial supporter" , "Angel" , "A supporter or a betting man" , "Sponsor" , "'Supporter, usually provides finance (6)'" .)