Strings of beads on the counter (6)
I believe the answer is:
abacus
'counter' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for abacus that I've seen before include "Counting machine" , "Simple calculating device" , "Counting device" , "means of multiplying" , "An ancient counting frame with beads" .)