胶

Left radical written as 月 here is actually the flesh radical 肉 (also drawn ⺼) — visually identical to the moon character but semantically the body indicator. Marks 胶 as something derived from animal tissue: traditional Chinese glue was boiled down from hides and bones. Same radical anchors 肝 (liver), 肠 (intestines), 肌 (muscle), 腿 (leg).

Right phonetic 交 supplies the full sound jiāo with no drift. 交 itself depicts a person with crossed legs — 'to cross, to join'. The semantic flavour fits beautifully: glue is precisely what makes things join. Same phonetic appears in 校 (school), 较 (compare), 郊 (suburbs), 饺 (dumpling).