An affair that does have importance (6)
I believe the answer is:
matter
This clue might be a double definition.
'an affair that does' is the first definition.
'matter' can be an answer for 'an affair' (synonyms). I am not certain of the remainder of the definition.
'importance' is the second definition.
(thesaurus)
'have' acts as a link.
Can you help me to learn more?
(Other definitions for matter that I've seen before include "Substance as opposed to spirit" , "It occupies space, has substance" , "Affair; be important" , "See 18" , "Physical substance" .)