Choose to participate (3,2)

I think it could be either:

Which length description are you looking for?:

3,2

opt in

'choose to participate' is the definition.
(I've seen this in another clue)

This is the entire clue.

(Other definitions for opt in that I've seen before include "be involved voluntarily" , "Choose to be included" , "Join voluntarily" , "Choose to participate" , "Choose to take part" .)

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.