。
She swatted the fly with the newspaper — smack!
Literal
She [topic-は] newspaper [with-で] fly [object-を] smack swatted.
ピシャっと is a sound mimetic (擬音語) for a sharp, flat slapping sound — the impact of newspaper against surface. It captures the satisfying 'smack' of a successful swat. ハエ (蝿) is the Japanese word for 'fly' (the insect), commonly written in katakana. The instrumental で marks the newspaper as the weapon.