Too dismal, sordid houses (4)
I believe the answer is:
also
'too' is the definition.
(synonyms)
'dismal sordid houses' is the wordplay.
'houses' says the answer is hidden in the clue (part of the clue houses the answer).
'ALSO' is hidden in the letters of 'dismal sordid'.
(Other definitions for also that I've seen before include "admitted to Royal Society > too" , "Old" , "in accompaniment" , "on top" , "item's rarely used now for this" .)