Core reading 压 covers physical and figurative pressing: 压力 (pressure/stress), 血压 (blood pressure), 镇压 (to suppress), 压岁钱 (lucky money). Almost every compound takes this reading.
mistakes
Don't confuse with the second reading 压 (fourth tone), which is bound to a tiny set: 压根儿 (not at all) and 压马路 (to stroll the streets). If you're talking about physical pressing, voltage, or stress, it's always 压.
Cliff radical on top - the indexing radical, picturing an overhanging rock face. Here it functions as the heavy thing pressing down from above, embodying the meaning of 压 (to press, to crush). Same radical heads characters of weight and shelter like 厌 (loathe) and 厨 (kitchen).
Earth pinned beneath the cliff - what is being compressed. Strokes assigned here include 土 (3 strokes) plus a residual dot that simplification kept from the traditional 壓; standalone 土 is 3 strokes, here 4 because of that fused dot. The image 'cliff over earth' captures the meaning of crushing pressure.
