Cat, then dog, stirred up pockets of disaster (3,2,3)
I believe the answer is:
act of god
'disaster' is the definition.
(I have seen 'Natural disaster' mean 'act of god' so perhaps 'disaster' could also mean 'act of god')
'cat then dog stirred up pockets of' is the wordplay.
'then' says to put letters next to each other.
'stirred up' indicates an anagram (letters get stirred up or mixed).
'pockets' indicates putting letters inside.
'cat'+'dog'='catdog'
'catdog' anagrammed gives 'actgod'.
'actgod' enclosing 'of' is 'ACT OF GOD'.
(Other definitions for act of god that I've seen before include "Natural catastrophe, force majeure" , "deus ex machina?" , "Inescapable happening" , "Unforeseeable accident" , "Uncontrollable natural event like earthquate" .)