Sinister old male in the States accepting Oscar (7)
I believe the answer is:
ominous
'sinister' is the definition.
(I know that sinister can be written as ominous)
'old male in the states accepting oscar' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'male' becomes 'm' (common abbreviation).
'the states' becomes 'US' (abbreviation for the United States).
'accepting' means one lot of letters goes inside another (inserted letters are accepted).
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'in'+'us'='inus'
'inus' placed around 'o' is 'inous'.
'o'+'m'+'inous'='OMINOUS'
(Other definitions for ominous that I've seen before include "Inauspicious" , "Portending bad things" , "'Sinister, baleful (7)'" , "Sinister-looking" , "Threatening or foreshadowing evil or tragedy" .)