What must make these worse? Anger must (9)
I believe the answer is:
arguments
'what must make these worse? anger must' is the definition.
The definition suggests an adverb but the answer is not.
'what must make these worse? anger must' is the wordplay.
'what must make these worse?' is an anagram indicator (the word makes the anagrammed letters worse).
'anger'+'must'='angermust'
'angermust' with letters rearranged gives 'ARGUMENTS'.
(Other definitions for arguments that I've seen before include "Contentious discussions" , "Discussions or quarrels" , "Tiffs" , "Heated discussions" , "spats" .)