Oscar, trophy unusually bagged by more sinister wit (7,6)
I believe the answer is:
dorothy parker
'wit' is the definition.
'oscar trophy unusually bagged by more sinister' is the wordplay.
'oscar' becomes 'o' (phonetic alphabet: alpha, bravo, charlie etc.).
'unusually' indicates an anagram.
'bagged by' indicates putting letters inside.
'more sinister' becomes 'darker'.
'o'+'trophy'='otrophy'
'otrophy' with letters rearranged gives 'orothyp'.
'orothyp' going inside 'darker' is 'DOROTHY PARKER'.
(Other definitions for dorothy parker that I've seen before include "Witty 20th century American writer" , "American humorous writer" .)