The term 'CERTAIN SHOOTER' can be broken down into four crossword solutions: PEA (3 letters), AGATE (5 letters), SLR (3 letters), and CATSEYE (7 letters). PEA is a type of edible seed, AGATE is a type of banded chalcedony, SLR stands for Single Lens Reflex, and CATSEYE is a type of optical lens. Together, these solutions form the phrase 'Certain Shooter, ' which refers to a type of camera that uses an SLR lens with a CATSEYE aperture and a PEA-sized shutter.