Clement largely in December, after vacation turning unsettled (7)
I believe the answer is:
rattled
'unsettled' is the definition.
(rattled can mean unsettled or unnerved)
'clement largely in december after vacation turning' is the wordplay.
'clement' becomes 'Attlee' (prime minister Clement Attlee).
'largely' means to remove the last letter.
'in' indicates putting letters inside.
'after vacation' means to remove the middle letters (the inside letters must vacate).
'turning' says the letters should be written in reverse.
'december' with its centre taken out is 'dr'.
'dr' reversed gives 'rd'.
'attlee' with its last letter taken off is 'attle'.
'attle' put into 'rd' is 'RATTLED'.
(Other definitions for rattled that I've seen before include "Hot and bothered, perturbed" , "Worried, irritated" , "Made a series of clattering sounds" , "What some snakes did" , "Agitated or flustered by child's toy?" .)