Discrepancy (8)
'discrepancy' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for variation that I've seen before include "Departure from the norm" , "Discrepancy" , "Change, difference" , "Slight difference" , "Slight change" .)
'discrepancy' is the definition.
(I know that discrepancy can be written as variance)
This is the entire clue.
(Other definitions for variance that I've seen before include "Not the main attraction" , "Difference, discrepancy" , "disagreement" , "Change" , "Dissension" .)