Eccentric let us in with implement (7)
I believe the answer is:
utensil
'implement' is the definition.
(I know that utensil is a type of implement)
'eccentric let us in' is the wordplay.
'eccentric' indicates an anagram.
'let'+'us'+'in'='letusin'
'letusin' is an anagram of 'UTENSIL'.
'with' is the link.
(Other definitions for utensil that I've seen before include "A tool for household use" , "Mandolin, perhaps" , "A kitchen instrument or container" , "Let us in (anag) -- implement" , "Useful tool" .)