2 succeeding often on the radio — as another? (4)

I believe the answer is:

bach

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'2' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

I cannot understand how the remainder of the clue works.

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(Other definitions for bach that I've seen before include "endearing Welsh appellation" , "Musical family" , "JS --, baroque composer" , "Goldberg Variations composer, d. 1750" , "Relating to stars" .)

I've seen this clue in The Guardian.

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