Rest at North Head? That's right! (4)
I believe the answer is:
lien
'right' is the definition.
(legal right)
'rest at north head?' is the wordplay.
'rest' becomes 'lie' (lying is a kind of resting).
'at' is a charade indicator (letters next to each other).
'head?' suggests taking the first letters (I've seen 'heads of' mean this).
The first letter of 'north' is 'n'.
'lie'+'n'='LIEN'
'that's' is the link.
(Other definitions for lien that I've seen before include "Legal right to detain property" , "Legal right over the Nile" , "Legal claim on the property of another" , "The right to take property if an obligation is not met" , "Right to another's property, if an obligation is not discharged" .)