Learning about island in French river (5)
I believe the answer is:
loire
'french river' is the definition.
(I've seen this before)
'learning about island' is the wordplay.
'learning' becomes 'lore' (I've seen this before).
'about' means one lot of letters goes inside another.
'island' becomes 'i'.
'lore' going around 'i' is 'LOIRE'.
'in' is the link.
(Other definitions for loire that I've seen before include "department in France" , "Longest river in France" , "River flowing through Tours and Nantes" , "banker" , "European river" .)