Cover up a cloak (6)
I believe the answer is:
mantle
I believe this clue is a double definition.
'cover up' is the first definition.
(thesaurus)
'a cloak' is the second definition.
(I know that mantle is a type of cloak)
(Other definitions for mantle that I've seen before include "Lament in loose cloak" , "Loose cloak, shawl" , "Gas lamp part; cloak" , "Robe or gas-lamp fitting" , "Cloak and shelf over the fireplace" .)