Front of some fairly good houses subsiding (7)
I believe the answer is:
descent
'subsiding' is the definition.
(thesaurus)
'front of some fairly good houses' is the wordplay.
'front of' says to take the initial letters (the letter at the front of the word).
'fairly good' becomes 'decent' (I've seen this before).
'houses' is an insertion indicator.
The first letter of 'some' is 's'.
's' put within 'decent' is 'DESCENT'.
(Other definitions for descent that I've seen before include "Coming down" , "Fall" , "Drop" , "Slope leading from top" , "Derivation from an ancestor - going down" .)