Spain and Portugal not initially part of Russia (6)
I believe the answer is:
iberia
'spain and portugal' is the definition.
(I've seen this in another clue)
'not initially part of russia' is the wordplay.
'not initially' means to remove the first letter.
'part of russia' becomes 'siberia' ('Siberia' is part of 'russia').
'siberia' with its first letter removed is 'IBERIA'.
(Other definitions for iberia that I've seen before include "Great European peninsula containing Spain and Portugal" , "Spain and Portugal (6)" , "Spain's national flag-carrying airline" , "European region" , "Peninsula housing Spain and Portugal" .)