Puts foot down on hallmarks (6)
I believe the answer is:
stamps
'hallmarks' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for stamps that I've seen before include "Brings foot heavily to the ground, as in anger" , "Imprints" , "Puts the foot down hard, in temper perhaps" , "creates an impression" , "Puts the foot down on letters" .)