Decoration worn on one's chest (6)
I believe the answer is:
tiepin
'decoration' is the definition.
(tiepin is a kind of decoration)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for tiepin that I've seen before include "Gent's accessory for an accessory" , "Fixer for neckwear" , "Ornamental securer" , "Fastener for strip around the neck" , "It's used to hold neckwear in place" .)