Changes involving a good number of digressions (8)
I believe the answer is:
vagaries
'number of digressions' is the definition.
(a vagary is a digression or unexpected change)
'changes involving a good' is the wordplay.
'changes' becomes 'varies' ('vary' can be a synonym of 'change').
'involving' means one lot of letters goes inside another.
'good' becomes 'g' (abbreviation).
'a'+'g'='ag'
'varies' enclosing 'ag' is 'VAGARIES'.
(Other definitions for vagaries that I've seen before include "Capricious acts or ideas" , "uncertainties" , "Whims" , "Unpredictable acts" , "Unpredictable occurrences" .)