More impressive kitchen implement under discussion (7)
I believe the answer is:
greater
'more impressive' is the definition.
'kitchen implement under discussion' is the wordplay.
'kitchen implement' becomes 'grater' (I've seen this before).
'under discussion' indicates a 'sounds like' (homophone) clue.
'grater' sounds like 'GREATER'.
(Other definitions for greater that I've seen before include "More extensive" , "Less small" , "more imposing scale" , "Most of it was formerly part of 1 across" , "Larger or more outstanding" .)