Right result upset cattle thief (7)
I believe the answer is:
rustler
'cattle thief' is the definition.
(synonyms)
'right result upset' is the wordplay.
'right' becomes 'r' (common abbreviation).
'upset' is an anagram indicator.
'result' anagrammed gives 'ustler'.
'r'+'ustler'='RUSTLER'
(Other definitions for rustler that I've seen before include "Stealer of livestock" , "Stock taker?" , "Cattle-thief" , "Cattle thief" , "Livestock thief" .)