Inventor is extremely logical (4)
I believe the answer is:
bell
'inventor' is the definition.
(I've seen this before)
'is extremely logical' is the wordplay.
'is' becomes 'be'.
'extremely' means to remove the middle letters.
'logical' with its middle removed is 'll'.
'be'+'ll'='BELL'
(Other definitions for bell that I've seen before include "Boxing match signal" , "It rings when struck" , "ring" , "Metal instrument" , "Chime" .)