Because it's followed by a shoot-out, indeed (8)
I believe the answer is:
forsooth
'indeed' is the definition.
(synonyms)
'because it's followed by a shoot-out' is the wordplay.
'because' becomes 'for' (I've seen this in other clues).
'it's followed by' means one lot of letters go next to another.
'out' indicates an anagram (out can mean wrong or inaccurate).
'shoot' with letters rearranged gives 'sooth'.
'for'+'sooth'='FORSOOTH'
(Other definitions for forsooth that I've seen before include "Indeed (archaic)" , "certainly" , "truly" , "In truth (arch)" , "Marry" .)