The French understand a person who rents (6)
I believe the answer is:
lessee
'a person who rents' is the definition.
(I've seen this before)
'the french understand' is the wordplay.
'the french' becomes 'les' (les is the in french).
'understand' becomes 'see' ('see' can be a synonym of 'understand').
'les'+'see'='LESSEE'
(Other definitions for lessee that I've seen before include "Tenant who holds a lease" , "One renting a property" , "Who pays the rent" , "One holding lease on property" , "I have to deal with letter" .)