Similarity seen with silk pants (8)
I believe the answer is:
likeness
'similarity' is the definition.
(likeness is a kind of similarity)
'seen with silk pants' is the wordplay.
'with' is a charade indicator (letters next to each other).
'pants' indicates anagramming the letters (UK informal term for 'nonsense' or 'rubbish').
'seen' after 'silk' is 'silkseen'.
'silkseen' anagrammed gives 'LIKENESS'.
(Other definitions for likeness that I've seen before include "depiction" , "Good portrait" , "Resemblance" , "Similarity in appearance" , "Similarity - faithful portrait" .)