Set represented, after trendy promotion, as an alternative (7)
I believe the answer is:
instead
'as an alternative' is the definition.
(synonyms)
'set represented after trendy promotion' is the wordplay.
'represented' is an anagram indicator.
'after' is a charade indicator (letters next to each other).
'trendy' becomes 'in' ('in' can mean fashionable).
'promotion' becomes 'ad' (short for advert).
'set' is an anagram of 'ste'.
'ste' put after 'in' is 'inste'.
'inste'+'ad'='INSTEAD'
(Other definitions for instead that I've seen before include "for a change" , "Alternatively" , "Stained (anag)" , "As a substitute" , "use this as a replacement" .)