Underlease is crafty, with tenant finally moving east (6)
I believe the answer is:
sublet
'underlease' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for sublet that I've seen before include "Rent secondarily" , "Rent all or part of a rented property to another person" , "Lease all or part of a rented property to another" , "get help to pay the rent, maybe" , "Rent out what one has rented" .)