The xìng reading is the 'interest / mood' family: 兴趣 (interest), 高兴 (happy), 尽兴 (to one's heart's content), 扫兴 (to have one's spirits dampened), 即兴 (impromptu, done on a whim). For the rise / flourish sense see the xīng reading.
Bottom indexing radical 八, two diverging strokes, originally a splitting motion (the source of 'eight'). Here it sits as a stylised base, the two splayed feet under the rising figure. The placement is somewhat arbitrary after simplification; the pre-reform form was indexed under 臼.
semantic
⺍xiǎo
small dots; raised hands
Top three dots, the radical-supplement form sometimes called 'small dots' or 'raised hands'. In 兴 they are the simplified residue of four hands raising up an object: traditional 興 had hands gripping and lifting. The dots preserve the lifting-hands imagery in compressed form.
Middle single horizontal, representing the object being lifted by the hands above. In traditional 興 this slot held a more complex middle with a framed core; the 1956 simplification flattened everything to one bar. A clean dividing line between hands and base.
