Anguished king's US subject accepting award (7)
I believe the answer is:
macbeth
'anguished king's' is the definition.
(king in Shakespeare play)
'us subject accepting award' is the wordplay.
'us subject' becomes 'math' (US name for mathematics).
'accepting' indicates putting letters inside (inserted letters are accepted).
'award' becomes 'CBE' (Commander of the Order of the British Empire award).
'math' placed around 'cbe' is 'MACBETH'.
(Other definitions for macbeth that I've seen before include "bloody drama" , "Shakespeare's Scottish play, considered unlucky" , "Ill-fated Shakespearean king" , "In sleep murderer" , "play with tragic results" .)