He is second on this list (8,5)
I believe the answer is:
periodic table
'he is second on this list' is the definition.
'periodic table' can be an answer for 'list' (I have seen 'Elementary list' mean 'periodic table' so perhaps 'list' could also mean 'periodic table'). I'm not sure about the remainder of the definition.
'on this list' is the wordplay.
'on this' becomes 'periodic' (I can't explain this - if you can you should believe this answer much more).
'list' becomes 'table' (I've seen this before).
'periodic'+'table'='PERIODIC TABLE'
(Other definitions for periodic table that I've seen before include "Chart of elements" , "Elementary information" , "Arrangement of chemical elements" , "List of elements arranged by atomic number" , "Elementary list" .)