A great deal, decimal? (5)

I believe the answer is:

often

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

'a great deal' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for often that I've seen before include "In many instances" , "Regularly" , "on many occasions" , "A great deal" , "Frequently, at short intervals" .)

I've seen this clue in The Telegraph.

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.