Fine period in which tin is shaken (6)
I believe the answer is:
dainty
'fine' is the definition.
('dainty' can be a synonym of 'fine')
'period in which tin is shaken' is the wordplay.
'period' becomes 'day' (day is a kind of period).
'in which' indicates putting letters inside.
'is shaken' indicates an anagram.
'tin' is an anagram of 'int'.
'day' going around 'int' is 'DAINTY'.
(Other definitions for dainty that I've seen before include "Delicately small and pretty" , "Titbit, delicacy" , "sensitive" , "Delicate, neat" , "Piece of cake!" .)