Say something is hard to do
This pattern says an action is hard or difficult to do.
JLPTN5
verb (masu-stem) + にくい~ [masu-stem] + nikui
[action] is hard to do
Take a verb's polite stem (the part before ます) and add にくい to say it is hard to do. The whole thing behaves like an い-adjective, so it can describe a noun or end a sentence. Its opposite is やすい, which means easy to do.