目覚まし時計 (hiragana めざましどけい, romaji mezamashidokei)
Compound of 目覚まし (mezamashi, “waking, wakeup”) + 時計 (tokei, “clock”, the 連用形 (ren'yōkei, “continuative or stem form”) of verb 目覚ます mezamasu, “to wake up”).[1][2]The tokei changes to dokei as an instance of rendaku (連濁).
