"A terrible slob," I add, "hard to get rid of" (7)
I believe the answer is:
abolish
'get rid of' is the definition.
(synonyms)
'a terrible slob i add hard' is the wordplay.
'terrible' indicates an anagram.
'add' says to put letters next to each other.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'slob'+'i'='slobi'
'slobi' anagrammed gives 'bolis'.
'a'+'bolis'+'h'='ABOLISH'
'to' is the link.
(Other definitions for abolish that I've seen before include "Cancel or abrogate" , "Nullify" , "Scrap" , "Formally do away with" , "Put an end to (practice)" .)