More skittish, at no time fitted around unfinished rig (7)

I believe the answer is:

nervier

I'm a little stuck... Click here to teach me more about this clue!

'more skittish' is the definition.
Both the answer and definition are comparative adjectives. Perhaps you can see a link between them that I don't see?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Another definition for nervier that I've seen is " More anxious".)

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.