Squirm uneasily when entertaining a nobleman (7)
I believe the answer is:
marquis
'nobleman' is the definition.
(marquis is a kind of nobleman)
'squirm uneasily when entertaining a' is the wordplay.
'uneasily' indicates anagramming the letters.
'when entertaining' means one lot of letters goes inside another.
'squirm' anagrammed gives 'mrquis'.
'mrquis' enclosing 'a' is 'MARQUIS'.
(Other definitions for marquis that I've seen before include "toff" , "De Sade's noble rank" , "British nobleman" , "Continental aristocrat" , "European nobleman" .)