They write baroque poems in heartless covers (9)
I believe the answer is:
composers
'they write' is the definition.
The definition suggests an adverb but the answer is not.
'baroque poems in heartless covers' is the wordplay.
'baroque' is an anagram indicator (baroque can mean fancy or complex).
'in' means one lot of letters goes inside another.
'heartless' suggests removing the centre.
'covers' with its centre taken out is 'cors'.
'poems' is an anagram of 'mpose'.
'mpose' put inside 'cors' is 'COMPOSERS'.
Can you help me to learn more?
(Other definitions for composers that I've seen before include "Mozart, Puccini" , "Chopin, Strauss etc." .)