Art as trendy, every other piece highly valued (5)
I believe the answer is:
rated
'highly valued' is the definition.
(I've seen this before)
'art as trendy every other piece' is the wordplay.
'every other piece' indicates alternate letters.
'art'+'as'+'trendy'='artastrendy'
The alternate letters of 'artastrendy' are 'RATED'.
(Other definitions for rated that I've seen before include "Had a high opinion of" , "Classified or graded" , "Castigated" , "Assessed in trade" , "Estimated, set at" .)