A positive response (3)
I believe the answer is:
yes
This clue is a double definition.
'a positive' is the first definition.
(thesaurus)
'response' is the second definition.
(I have seen 'Affirmative response' mean 'yes' so perhaps 'response' could also mean 'yes')
(Other definitions for yes that I've seen before include "Affirmative response" , "Aye" , "Agreed" , "I agree" , "Indeed" .)