Exploding pie middle: disaster area (9)
I believe the answer is:
epicentre
'disaster area' is the definition.
(I've seen this before)
'exploding pie middle' is the wordplay.
'exploding' is an anagram indicator.
'middle' becomes 'centre' (synonyms).
'pie' is an anagram of 'epi'.
'epi'+'centre'='EPICENTRE'
(Other definitions for epicentre that I've seen before include "Shocking scene" , "Earthquake's surface location" , "Focus of activity" , "a very disturbed place" , "Point at which earthquake reaches earth's surface" .)