Occasional piece of furniture in collection of chemical elements (8,5)
I believe the answer is:
periodic table
'collection of chemical elements' is the definition.
The definition and answer can be both groups as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'occasional piece of furniture' is the wordplay.
'occasional' becomes 'periodic' (I've seen this before).
'piece of furniture' becomes 'table' (table is a kind of piece of furniture).
'periodic'+'table'='PERIODIC TABLE'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for periodic table that I've seen before include "List of elements arranged by atomic number" , "List of chemical elements" , "Elementary list" , "Chart of elements" , "Arrangement of chemical elements" .)