Out of keeping, prom ripe for redevelopment (8)
I believe the answer is:
improper
'out of keeping' is the definition.
(thesaurus)
'prom ripe for redevelopment' is the wordplay.
'for redevelopment' indicates an anagram (I've seen this in other clues).
'prom'+'ripe'='promripe'
'promripe' is an anagram of 'IMPROPER'.
(Other definitions for improper that I've seen before include "unfit" , "Not in line with accepted standards of morality" , "Unfitting, out of place" , "Not fitting" , "Inappropriate" .)