Dolt is exceptionally unmoved (6)
I believe the answer is:
stolid
'unmoved' is the definition.
(thesaurus)
'dolt is exceptionally' is the wordplay.
'exceptionally' indicates anagramming the letters.
'dolt'+'is'='doltis'
'doltis' with letters rearranged gives 'STOLID'.
(Other definitions for stolid that I've seen before include "Impassive or apathetic" , "Not excitable or emotional" , "Hard to excite" , "'Calm and dependable, showing little emotion (6)'" , "Showing little or no interest or emotion" .)