Type of furniture to fill apartment above (8)
I believe the answer is:
flatpack
'type of furniture' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'fill apartment above' is the wordplay.
'fill' becomes 'pack' (packing is a kind of filling).
'apartment' becomes 'flat' (synonyms).
'above' is a charade indicator (letters next to each other) (in a down clue, some letters go above others).
'pack' after 'flat' is 'FLATPACK'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for flatpack that I've seen before include "(Of furniture) to be assembled by the buyer" , "Item for DIY assembly" , "In pieces ready to be assembled by the purchaser" , "Boxed for DIY assembly" , "such as DIYer gets" .)