Eccentric owns teeth sharpener (9)
I believe the answer is:
whetstone
'sharpener' is the definition.
(I've seen this before)
'eccentric owns teeth' is the wordplay.
'eccentric' indicates anagramming the letters.
'owns'+'teeth'='ownsteeth'
'ownsteeth' anagrammed gives 'WHETSTONE'.
(Other definitions for whetstone that I've seen before include "Sharpener" , "For sharpening edged tools or knives" .)