Rattled by death, calm Shakespearean character (4,7)
I believe the answer is:
lady macbeth
'shakespearean character' is the definition.
(I've seen this before)
'rattled by death calm' is the wordplay.
'rattled' indicates an anagram.
'by'+'death'+'calm'='bydeathcalm'
'bydeathcalm' anagrammed gives 'LADY MACBETH'.
(Other definitions for lady macbeth that I've seen before include "Ambitious Shakespearean character" , "Shakespearean female" , "Tragic figure" , "One promoted queen" , "Shakespearean sleepwalker" .)