He's number two in this organisation (8,5)
I believe the answer is:
periodic table
'number two in this organisation' 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?
'he's' is the wordplay.
I cannot really see how this works, but
'he' could be 'tab' and 'tab' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for periodic table that I've seen before include "Arrangement of chemical elements" , "List of chemical elements" , "Elementary list" , "Elementary information" , "Chart of elements" .)