One tree in the French island (2,5)
I believe the answer is:
la palma
'island' is the definition.
(Canary island)
'one tree in the french' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'tree' becomes 'palm' (palm is a kind of tree).
'in' indicates putting letters inside.
'the french' becomes 'la' (one of the French words for 'the').
'a'+'palm'='apalm'
'apalm' inserted into 'la' is 'LA PALMA'.
(Other definitions for la palma that I've seen before include "A Canary Island" , "Island of the Canaries" , "one of the Canary Islands" , "Spanish island" .)