Final goal? (3)

I think it could be either:

Which length description are you looking for?:

end

I believe this clue is a double definition.

'final' is the first definition.
(synonyms)

'goal?' is the second definition.
(both can mean a purpose)

(Other definitions for end that I've seen before include "Finish, close" , "Aim - point - finish" , "Terminus" , "Fine" , "Conclusion, finish" .)

Want a hint initially instead of a full solution? Install my app