Fashionable pet hopelessly clumsy (5)
I believe the answer is:
inept
'clumsy' is the definition.
('inept' can be a synonym of 'clumsy')
'fashionable pet hopelessly' is the wordplay.
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
'hopelessly' is an anagram indicator.
'pet' anagrammed gives 'ept'.
'in'+'ept'='INEPT'
(Other definitions for inept that I've seen before include "Blundering" , "Awkward, clumsy" , "Amateurish" , "Clumsy, out of place" , "Unskilful or unsuitable" .)