noun
rathole; mousehole
A hole made by a rat or mouse, or a hole as small as one made by such a rodent.
壁に鼠穴を見つけた。
I found a rathole in the wall.
鼠穴からネズミが出入りしている。
Rats are going in and out of the rathole.
ネズミ is the animal itself (rat/mouse), while 鼠穴 specifically refers to the hole it makes.
穴 is a general hole; 鼠穴 is specifically a hole made by or associated with rats/mice.
Compound of 鼠 (nezumi, 'rat/mouse') and 穴 (ana, 'hole'). The reading ねずみあな is a straightforward combination.