Informal (and informative?) entertainment (5)

I believe the answer is:

telly

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'entertainment' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for telly that I've seen before include "Familiar name for TV" , "One of the media" , "TV (colloq.)" , "Television" , "- - Savalas" .)

I've seen this clue in the Evening Standard.

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