Caught Reagan out in slaughter (7)
I believe the answer is:
carnage
'slaughter' is the definition.
(I know that slaughter can be written as carnage)
'caught reagan out in' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'out' is an anagram indicator (out can mean wrong or inaccurate).
'in' is an insertion indicator.
'reagan' anagrammed gives 'arnage'.
'c' inserted within 'arnage' is 'CARNAGE'.
(Other definitions for carnage that I've seen before include "Blood bath" , "Bloodshed" , "Bloodbath" , "Multiple killing" , "Widespread killing" .)