Deity returning a useful device (5)
I believe the answer is:
diana
'deity' is the definition.
(Diana is an example)
'returning a useful device' is the wordplay.
'returning' says the letters should be written in reverse.
'a' becomes 'an'.
'useful device' becomes 'aid' (I can't explain this - if you can you should give a lot more credence to this answer).
'an'+'aid'='anaid'
'anaid' written backwards gives 'DIANA'.
Can you help me to learn more?
(Other definitions for diana that I've seen before include "MONKEY" , "Roman goddess of the moon and hunting" , "Roman huntress goddess" , "Woman" , "Girl" .)