心細いな
 

What is the final な? The only な as final I know is the negative of a command. There can be also the だ transformed into な before a の in informal questions...but anyway this is an i adjective so can't be だ.

I ran out of ideas :)
P.S. It is the title of a song so there is no rest of a phrase to provide.

That な is a variant of ね placed at the end of a sentence implying reflection. (I trust that you understand by now that "心細い", by itself, is a sentence with a subject hidden within.). This な is often written and pronounced also as なあ or なぁ.

Thank you very much.