Girl not wanting a financial backer (5)
I believe the answer is:
Here is my best explanation:
'a financial backer' is the definition.
(I've seen this before)
'girl not wanting' is the subsidiary indication.
'girl' becomes 'ange'.
'not wanting' becomes 'l' (I can't justify this - if you can you should believe this answer much more).
(Other definitions for angel that I've seen before include "old coin", "Guardian spirit; theatre investor", "Spiritual being - financial backer", "Messenger < is a nurse", "Old coin; theatre investor", "lady (very kind)", "Investor in a theatrical production", "Theatre supporter", "somewhere on the Northern Line" and "somewhere in Islington".)