Alone, a tenant keeps tidy (6)
I believe the answer is:
neaten
'tidy' is the definition.
(I know that tidy can be written as neaten)
'alone a tenant keeps' is the wordplay.
'keeps' indicates a hidden word.
'NEATEN' is hidden within 'alone a tenant'.
(Other definitions for neaten that I've seen before include "Trim" , "Make tidy" , "Straighten up" , "set in order" , "Make orderly" .)