Inserting end of chisel, make bigger hole in sphere (5)
I believe the answer is:
realm
'sphere' is the definition.
(I know that realm is a type of sphere)
'inserting end of chisel make bigger hole' is the wordplay.
'inserting' is an insertion indicator.
'end of' suggests the final letters.
'make bigger hole' becomes 'ream' (ream can mean to widen a hole).
The final letter of 'chisel' is 'l'.
'l' inserted inside 'ream' is 'REALM'.
'in' acts as a link.
(Other definitions for realm that I've seen before include "Area of interest/activity" , "Country" , "Kingdom, or field of activity" , "Kingdom, domain" , "Area of influence" .)