Whims (4)
'whims' is the definition.
('vagary' can be a synonym of 'whim')
This is the entire clue.
(Other definitions for vagaries that I've seen before include "Unexplained changes" , "uncertainties" , "Unpredictable occurrences" , "Whims" , "unpredictable changes" .)
(Other definitions for fads that I've seen before include "Short-lived crazes" , "Fashions or vogues" .)