Catalyzes the first oxidative step of the phenylpropanoid pathway in higher plants by transforming trans-cinnamate into p-coumarate (By similarity). The compounds formed by this pathway are essential components for lignification, pollination, and defense against ultraviolet light, predators and pathogens (By similarity). (E)-cinnamate + O2 + reduced [NADPH--hemoprotein reductase] = (E)-4-coumarate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Phenylpropanoid metabolism; trans-4-coumarate biosynthesis; trans-4-coumarate from trans-cinnamate: step 1/1. By fungal elicitor. Belongs to the cytochrome P450 family.