シュウ, おそ.う, かさ.ね, そい
attack, advance on, succeed to, pile, heap
JLPT1 G7 S22 F1130
龖 is 龍 dragon (doubled) → dragons pressed closely together in flight. 襲 combines 龍 (an abbreviated form# of 龖) + 衣 clothing → wear layers of clothing (← double/pile up garments) → *inherit*; *succeed to* (← add goods, offices etc. to those already in one's possession). Also, *attack*; *sweep over* and *seize* (← attack like dragons in flight).
[Full Kanji Etymology List]