Unusual knickknack (5)
I believe the answer is:
curio
'unusual knickknack' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for curio that I've seen before include "Intriguing object worth collecting" , "Oddity, rarity" , "Bygone" , "Object of interest because it is a rare or unusual" , "Unusual, intriguing object" .)