lead
鈆 centers on the metal lead, a heavy and soft material. The single given meaning is straightforward and does not require further conceptual linking.
鈆 is a historical variant of 鉛 (lead). It combines the metal radical 金 with 公, which likely served as a phonetic component in this older form.
The metal radical 金 tells you it is a metal, and the right side 公 looks like a heavy, squat block. Picture a public (公) block of lead metal (金) that is too heavy to lift.
For エン, imagine an English lead pencil: the 'en' in 'pencil' sounds like エン, and the pencil's lead core connects to the meaning.