The Mendips housing fix (5)
I believe the answer is:
emend
'fix' is the definition.
(thesaurus)
'the mendips housing' is the wordplay.
'housing' indicates the answer is hidden within the clue (part of the clue houses the answer).
'EMEND' is hidden within 'the mendips'.
(Other definitions for emend that I've seen before include "Improve (texts)" , "Rectify" , "Correct and improve the text" , "make an improvement" , "Remove faults from" .)