Trendies could be introduced (8)
I believe the answer is:
inserted
'introduced' is the definition.
('insert' can be a synonym of 'introduce')
'trendies could be' is the wordplay.
'could be' indicates anagramming the letters.
'trendies' with letters rearranged gives 'INSERTED'.
(Other definitions for inserted that I've seen before include "Introduced" , "Put in" , "taken out? The opposite" .)