Smellier model replaced for model ultimately more lissome (8)

I believe the answer is:

slinkier

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

'smellier' is the definition.
Both the answer and definition are comparative adjectives.
Perhaps they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

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.