Trendy record but ultimately useless (5)
I believe the answer is:
inept
'useless' is the definition.
(I've seen this in another clue)
'trendy record but ultimately' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'record' becomes 'EP' (abbreviation for extended play record).
'ultimately' suggests the final letters.
The last letter of 'but' is 't'.
'in'+'ep'+'t'='INEPT'
(Other definitions for inept that I've seen before include "Amateurish" , "Awkward, clumsy" , "Unskilful or unsuitable" , "Blundering" , "Standard required in a piece of work (colloq.)" .)