Large hole right at side of case (6)
I believe the answer is:
crater
'large hole' is the definition.
(large hole in the ground)
'right at side of case' is the wordplay.
'right' becomes 'r' (common abbreviation).
'at side of' says to put letters next to each other.
'case' becomes 'crate' (crating is a kind of casing).
'r' put after 'crate' is 'CRATER'.
(Other definitions for crater that I've seen before include "Volcano opening" , "Bowl-shaped cavity as on volcano peak" , "Capital of Virginia" , "Volcanic cavity" , "Bomb-hole" .)