Purcell has composed, despite being gloomy (10)
I believe the answer is:
sepulchral
'being gloomy' is the definition.
('sepulchral' can be a synonym of 'gloomy')
'purcell has composed' is the wordplay.
'composed' is an anagram indicator.
'purcell'+'has'='purcellhas'
'purcellhas' with letters rearranged gives 'SEPULCHRAL'.
'despite' is the link.
(Other definitions for sepulchral that I've seen before include "from the grave" , "offering gloomy tones" .)