Let learner relax (5)
I believe the answer is:
lease
'let' is the definition.
(as in to lease or let a building)
'learner relax' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'relax' becomes 'ease' (eg to ease a restriction is to relax it).
'l'+'ease'='LEASE'
(Other definitions for lease that I've seen before include "Letting contract" , "Rent -- easel (anag)" , "Let out, hire" , "Renting contract" , "Let (property)" .)