Number fifty though follows forty-nine, ultimately (6)

I believe the answer is:

eleven

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

'number fifty' is the definition.
'eleven' can be an answer for 'fifty' (thesaurus). I'm not certain of the 'number' bit.

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

Can you help me to learn more?

(Other definitions for eleven that I've seen before include "Enough for a soccer side" , "Number killed in the Peterloo massacre" , "Cardinal" , "Time for the mid-morning tea break?" , "Number on a side (6)" .)

I've seen this clue in The Telegraph.

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