Fitting comment a reply makes (13)
I believe the answer is:
complementary
'fitting' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I don't see?
'comment a reply makes' is the wordplay.
'makes' indicates anagramming the letters.
'comment'+'a'+'reply'='commentareply'
'commentareply' is an anagram of 'COMPLEMENTARY'.
Can you help me to learn more?
(Other definitions for complementary that I've seen before include "Kind of 2 down treatment -- temple acronym (anag)" , "Interrelating, completing" , "Mutually enhancing" , "Matching" .)