European person putting son on throne (4)

I believe the answer is:
slav
'european' is the definition.
(I've seen this before)
'son on throne' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'throne' becomes 'lav' (both can informally mean toilet).
's'+'lav'='SLAV'
'person putting' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for slav that I've seen before include "Native of eastern Europe, perhaps" , "eg a Pole" , "Native of eastern Europe or northwestern Asia" , "Person speaking one of related languages of Euro-Asian border" , "Eastern European" .)
