Instrument at home in dark red cover (8)
I believe the answer is:
clarinet
'instrument' is the definition.
(clarinet is a kind of instrument)
'home in dark red cover' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'in' means one lot of letters goes inside another.
'dark red cover' becomes 'claret' (I am not sure about this - if you are sure you should believe this answer much more).
'in' put into 'claret' is 'CLARINET'.
'at' is the link.
Can you help me to learn more?
(Other definitions for clarinet that I've seen before include "member of orchestra" , "Blow that!" , "It's for playing" , "23 instrument" , "Wind instrument made from Clare tin" .)