The answer is "Daag", which was released in 1973 and marked the acting debut of Kader Khan, though his role in the film was uncredited. This social drama, directed by Yash Chopra, stars Rajesh Khanna and Sharmila Tagore in the lead roles, exploring themes of love, betrayal, and societal prejudices.
The Legendary Journey of Kader Khan: A Quiz on the Maestro of Indian Cinema