Shout I didn’t hear that’s upset poet (7)
I believe the answer is:
shelley
'poet' is the definition.
(Percy Bysshe Shelley 1792-1822)
'shout i didn't hear that's upset' is the wordplay.
'shout' becomes 'yell' (yelling is a kind of shouting).
'i didn't hear that's' becomes 'eh's' ('eh?' is used to ask someone to repeat something).
'upset' says the letters should be written in reverse.
'yell'+'ehs'='yellehs'
'yellehs' backwards is 'SHELLEY'.
(Other definitions for shelley that I've seen before include "Ode to the West Wind poet" , "Mary - - (Gothick writer)" , "Author of Frankenstein" , "Writer of To a skylark" , "Percy Bysshe . . . . . . ., great English poet" .)