Climbs on the weighing machine (6)
I believe the answer is:
scales
I believe this is a double definition.
'climbs' is the first definition.
(scaling is a kind of climbing)
'the weighing machine' is the second definition.
(I've seen this before)
'on' acts as a link.
(Other definitions for scales that I've seen before include "Zodiac sign < covering fish" , "Weighing devices or fish flakes" , "Balance - climbs" , "Set of balances" , "They're found on fish" .)