Are you saying if you check a Hindi word, it doesn't show the definition? I have American English, Apple Dictionary, and Spanish. If I check a Spanish word, it shows the definition in Spanish. If that doesn't work with Hindi, try unchecking Hindi, then check it again. If that doesn't work, try Reset All Settings.
Go to Settings >General >Reset >Reset All Settings. This resets to default everything in Settings, including notifications, alerts, brightness, and clock settings like wake up alarms.