She's returning a helpful thing (5)
I believe the answer is:
diana
'she's' is the definition.
'returning a helpful thing' is the wordplay.
'returning' says the letters should be written in reverse.
'a' becomes 'an'.
'helpful thing' becomes 'aid' (I can't explain this - if you can you should believe this answer much more).
'an'+'aid'='anaid'
'anaid' backwards is 'DIANA'.
Can you help me to learn more?
(Other definitions for diana that I've seen before include "British princess" , "Girl" , "Roman equivalent of Artemis" , "Roman huntress goddess" , "Girl's name; goddess" .)