Hollow in end of canine may show this (7)
I believe the answer is:
dentine
'show this' is the definition.
The definition suggests a singular noun which matches the answer.
'hollow in end of canine' is the wordplay.
'hollow' becomes 'dent' (both can mean an impression or indentation).
'end of' indicates one should take the final letters.
The last letter of 'canine' is 'e'.
'dent'+'in'+'e'='DENTINE'
'may' acts as a link.
(Other definitions for dentine that I've seen before include "Material in teeth" , "bony material" , "which forms tooth" , "Tin need (anag.)" , "Substance of which teeth are mainly composed" .)