Contrast (10)
'contrast' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for comparison that I've seen before include "Assessment of differences" , "Similarity" , "Process of identifying differences" , "Analogy; likeness" , "distinction" .)
(Other definitions for difference that I've seen before include "Variation" , "Diversity" , "Variance; disagreement" , "Argument - dissimilarity" , "row" .)