Unpredictable state — storm is brewing (3-2-4)
I believe the answer is:
hit-or-miss
'unpredictable' is the definition.
(I've seen this in another clue)
'state storm is brewing' is the wordplay.
'state' becomes 'HI' (abbreviation for Hawaii).
'brewing' is an anagram indicator.
'storm'+'is'='stormis'
'stormis' anagrammed gives 'tormiss'.
'hi'+'tormiss'='HIT-OR-MISS'
(Other definitions for hit-or-miss that I've seen before include "Haphazard, random" , "Of method, erratic or random" .)