Emperor snatching victory: America uneasy (7)
I believe the answer is:
nervous
'uneasy' is the definition.
(I know that uneasy can be written as nervous)
'emperor snatching victory america' is the wordplay.
'emperor' becomes 'nero' (Roman emperor).
'snatching' means one lot of letters goes inside another.
'victory' becomes 'v'.
'america' becomes 'US' (United States).
'nero' enclosing 'v' is 'nervo'.
'nervo'+'us'='NERVOUS'
(Other definitions for nervous that I've seen before include "'Apprehensive, uneasy (7)'" , "Tense" , "Jittery" , "Twitchy" , "Stirred" .)