Queen welcomes in philosopher supported by old politician (4,6)
I believe the answer is:
mark antony
'old politician' is the definition.
The definition suggests a singular noun which matches the answer.
'queen welcomes in philosopher supported by' is the wordplay.
'queen' becomes 'Mary' (Mary I or Mary II).
'welcomes' indicates putting letters inside (in sense of 'invites in').
'in philosopher' becomes 'kant' (I am not sure about this - if you are sure you should believe this answer much more).
'supported by' becomes 'on' (something on something else is supported by it).
'kant'+'on'='kanton'
'mary' going around 'kanton' is 'MARK ANTONY'.
Can you help me to learn more?
(Other definitions for mark antony that I've seen before include "Roman politician and lover of Cleopatra" , "borrower of ears" , "classical role" , "general" .)