A measure of restraint (5)
I believe the answer is:
chain
I believe this clue is a double definition.
'a measure' is the first definition.
(unit equal to 22 yards)
'restraint' is the second definition.
(I know that chain is a type of restraint)
'of' is the link.
(Other definitions for chain that I've seen before include "Mountain range" , "Series of things linked together" , "distance for a run?" , "a sort of letter" , "Group of atoms" .)