The phrase "ostensible lead" refers to a person or thing that appears to be in a leading position or role, but may not necessarily be the actual leader or main focus. Full definition
Ostensible lead Ethan Chandler had already settled into a funk, and with the introduction of two new characters it felt like Penny Dreadful was still clearing its throat before getting on with the good stuff. (tv.avclub.com)
Jack Nicholson, already a two - time Academy Award winner (he'd later collect a third trophy in the 1990s), was paid a king's ransom for the role (his cut of the film's profits ran to an estimated $ 50 million) and received top billing above the movie's ostensible lead Michael Keaton. (theatlantic.com)
Nolan seems to think the Wally Pfister photography can sell any scene, whether it's one of the most boring chase sequences in a big budget film (but it's at twilight and Pfister makes it look great) or if it's ostensible lead Christian Bale and his romantic interest, Marion Cotillard, letting the rainy afternoon bring out their passions. (thestopbutton.com)