Nora often changed for this part of the day (9)
I believe the answer is:
afternoon
'this part of the day' is the definition.
(I've seen this before)
'nora often changed' is the wordplay.
'changed' indicates an anagram.
'nora'+'often'='noraoften'
'noraoften' anagrammed gives 'AFTERNOON'.
'for' acts as a link.
(Other definitions for afternoon that I've seen before include "No ante for this part of the day" , "Post-midday" , "half a day?" , "time for tea" , "several hours" .)