Clue: Old Hindu in a jiffy? (4)
Answer: JAIN
Explanation: Definition: Old Hindu
Ouch! The wordplay is an anagram (-'iffy') of 'in a j'-, with a (well-justified) question mark. But then Hinduism and Jainism, although both primarily Indian, are distinct religions, and I do not think the question mark covers that. There is the possible get-out that 'old Hindu' refers to the archaic meaning of any inhabitant of India.