Relax, loosen (4)
I believe the answer is:
ease
I believe this clue is a double definition.
'relax' is the first definition.
(eg to ease a restriction is to relax it)
'loosen' is the second definition.
(I've seen this in another clue)
(Other definitions for ease that I've seen before include "Allay" , "Poise or leisure" , "Relief" , "No trouble" , "Freedom from worries" .)