Kept America sullied externally (9)
I believe the answer is:
sustained
'kept' is the definition.
('sustain' can be a synonym of 'keep')
'america sullied externally' is the wordplay.
'america' becomes 'US' (United States).
'sullied' becomes 'stained' (synonyms).
'externally' indicates putting letters inside (some letters go on the outside of others).
'us' put within 'stained' is 'SUSTAINED'.
(Other definitions for sustained that I've seen before include "held up" , "Kept going, supported" , "Kept (something) going" , "Steadily maintained" , "bore" .)