Shackle produced by Roman soldiers seizing rebel leader (3,4)
I believe the answer is:
leg iron
'shackle' is the definition.
(shackle for a leg)
'roman soldiers seizing rebel leader' is the wordplay.
'roman soldiers' becomes 'legion' (group of soldiers in Ancient Rome).
'seizing' is an insertion indicator.
'rebel leader' becomes 'r' (I've seen this in other clues).
'legion' going around 'r' is 'LEG-IRON'.
'produced by' is the link.
(Other definitions for leg iron that I've seen before include "restriction put on pin" , "Fetter" , "which delays flight indefinitely" , "Ankle restraint for a prisoner" .)