high up 一般我们不把它看做词组.我们看一下文中的原句：The light was high up on the cliffs.那高高的峭壁上的光亮.这里的 up 和 后面的on the cliffs 连起来看.on the cliffs 意思是：在峭壁上,而high 表示高的.
以下是几个类似的例子,可以看出大概的用法吧?
He is very cocky,his tail sticking high up in the air.
他骄傲得不得了,尾巴翘到天上去了.
High up among the bulging clouds thunder went off like a gun.
在膨胀的高空云层中,象开炮似打着响雷.
The lights were charmingly disposed in coloured-paper lamps,high up among green boughs.
烛光都安在红绿颜色纸糊成的灯里,高高地挂在青枝绿叶之间.
The plane was nosing high up into the sky.
飞机正向上升入高空.
The town was built high up on the steep clay banks of a rapid stream.
镇址是在一条湍急的河流的陡峭河岸上.
Birds are flying high up in the air.
鸟儿在高空中飞翔.
Larks were warbling high up in the sky.
云雀在高空鸣唱.
我只能做到这么多了,