Rebuilt city mess affecting an entire body (8)
I believe the answer is:
systemic
'affecting an entire body' is the definition.
'rebuilt city mess' is the wordplay.
'rebuilt' indicates an anagram.
'city'+'mess'='citymess'
'citymess' anagrammed gives 'SYSTEMIC'.
(Other definitions for systemic that I've seen before include "Relating to the whole organism" , "Affecting a body, institution, etc as a whole" , "insecticide" , "Relating to a complex whole" , "City mess (anag)" .)