I can’t repair the hole in the case (6)
I believe the answer is:
action
'case' is the definition.
(synonyms)
'i can't repair the hole in the' is the wordplay.
'repair' indicates an anagram.
'the hole' becomes 'o'.
'in the' indicates putting letters inside.
'i'+'cant'='icant'
'icant' is an anagram of 'actin'.
'actin' enclosing 'o' is 'ACTION'.
(Other definitions for action that I've seen before include "exploit" , "A judicial proceeding brought by one party against another" , "Deed; armed conflict" , "Accomplishment" , "Battle or lawsuit, maybe" .)