Learning about island river (5)
I believe the answer is:
loire
'river' is the definition.
(I know that Loire is a river)
'learning about island' is the wordplay.
'learning' becomes 'lore' (both can mean tradition or knowledge).
'about' means one lot of letters goes inside another.
'island' becomes 'i' (geographical abbreviation).
'lore' placed around 'i' is 'LOIRE'.
(Other definitions for loire that I've seen before include "banker" , "River flowing through Tours and Nantes" , "Longest river in France" , "River of central France" , "flower abroad" .)