If you want a non-admin user to be able to clear the TYPO3 cache, then add this typoscript to the user's TSCONFIG:

options.clearCache.pages = 1
options.clearCache.system = 1
options.clearCache.all = 1

You can omit lines from the above to only allow clearing of the page cache. The above will allow a user to clear all of the caches that an admin user would be able to clear. For more information see posts by jokumer and Jozef Spisiak at StackOverflow.