Many kanji are composed of symbols that are also kanji in themselves; there are also radicals which are not kanji in isolation but appear in the same form in many characters.

That being said, the meaning (or meanings...) of a kanji cannot be derived from its parts, just like the meaning of an English word cannot be derived from the letters that appear in it.

Also, as a rule, the same character will be read differently in different contexts. E.g. 生きる _i_kiru "to live", 生まれる _uma_reru "to be born", 学生 gaku_sei_ "student".