Answer:
clever
Step-by-step explanation:
In this case, you are attempting to describe and compare two different people. Many words use superlatives to compare people like fast/faster/fastest. However, the word clever does not use superlatives. When comparing people's cleverness adverbs such as less, more, or most should be used. In this sentence, the adverb more is already used, so the base form of the word, clever, should be used.