It puts an end to any ill-feeling (7)
I believe the answer is:
panacea
'it puts an end to any ill-feeling' is the definition.
The definition suggests a singular noun which matches the answer.
'it puts an' is the wordplay.
I cannot really understand how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is present in the answer.
'an' could be 'a' and 'a' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for panacea that I've seen before include "Panpharmacon" , "A cure-all for diseases or troubles" , "that will cure anything" , "Cure for all things" , "Cure for all ills" .)