Popular record but ultimately unskilful (5)
I believe the answer is:
inept
'unskilful' is the definition.
(I've seen this before)
'popular record but ultimately' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'record' becomes 'EP' (abbreviation for extended play record).
'ultimately' indicates one should take the final letters.
The final letter of 'but' is 't'.
'in'+'ep'+'t'='INEPT'
(Other definitions for inept that I've seen before include "Unskilful, awkward" , "Amateurish" , "Standard required in a piece of work (colloq.)" , "Incompetent or awkward" , "Unskilful or unsuitable" .)