Seaside structure ripe for redevelopment (4)
I believe the answer is:
pier
'seaside structure' is the definition.
(I've seen this before)
'ripe for redevelopment' is the wordplay.
'for redevelopment' is an anagram indicator (letters developed into a new form).
'ripe' with letters rearranged gives 'PIER'.
(Other definitions for pier that I've seen before include "Landing stage; arch support" , "One jutting into sea" , "Part of airport terminal; breakwater" , "Supporting structure" , "Seaside platform" .)