South Mediterranean peninsula? No, it's in Russia (7)
I believe the answer is:
siberia
'it's in russia' is the definition.
('Siberia' is part of 'russia')
'south mediterranean peninsula?' is the wordplay.
'south' becomes 's' (abbreviation).
'mediterranean peninsula?' becomes 'iberia' (I've seen this before).
's'+'iberia'='SIBERIA'
'no' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for siberia that I've seen before include "chosen by Putin for no-frills travel?" , "Eastern part of Russia" , "Arctic region" , "Eastern region of Russia" , "Former place of exile for a Russian" .)