That is keeping scoundrel angry (5)
I believe the answer is:
irate
'angry' is the definition.
('irate' can be similar in meaning to 'angry')
'that is keeping scoundrel' is the wordplay.
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'keeping' is an insertion indicator.
'scoundrel' becomes 'rat' (I've seen this in other clues).
'ie' enclosing 'rat' is 'IRATE'.
(Other definitions for irate that I've seen before include "Livid" , "Boiling" , "Angry and incensed" , "Angry - furious" , "Angry, annoyed" .)