Clue: Regularly says Iran must be a major part of the world (4)
Answer: ASIA
Explanation: Definition:  a major part of the world 
"regularly" "s**A**y**S" **and then **"I**r**A**n" 
Doesn't work as the I and A of Iran should be the second and fourth letters for the "regularly" to be valid for both "says" and "Iran" (SINAI may have worked better, for example)