Frequently decimal? (5)

I believe the answer is:

often

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

'frequently' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

(Other definitions for often that I've seen before include "Frequently, many times" , "Frequently, habitually" , "A lot" , "Multiply" , "Commonly" .)

I've seen this clue in The Irish News, The Irish Independent, The Sun and The Globe and Mail.

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