Auction takes note of weighing device (5)
I believe the answer is:
scale
'weighing device' is the definition.
(I've seen this in another clue)
'auction takes note' is the wordplay.
'auction' becomes 'sale' (type of sale).
'takes' means one lot of letters goes inside another.
'note' becomes 'c' (musical note).
'sale' enclosing 'c' is 'SCALE'.
'of' acts as a link.
(Other definitions for scale that I've seen before include "Alec's (anag) -- graduation" , "Graduated table" , "Size ratio; skin flake" , "Deposit formed in a kettle or on teeth" , "Group of notes in ascending or descending order" .)