Don't mention it (2,7)
'don't mention it' is the definition.
(both can mean 'you're welcome')
This is all the clue.
(Other definitions for not at all that I've seen before include "Don't mention it!" , "By no means - polite disclaimer" , "Anything but!" , "You're welcome" , "forget it" .)
(Another definition for sore spot that I've seen is " Touchy subject: bruise, perhaps".)
'don't mention it' is the definition.
(phrases used when someone thanks you for something)
This is all the clue.
(Other definitions for no problem that I've seen before include "fine" , "Easy peasy!" , "Don't worry about it!" , "of course" .)