Nothing is held back in … (3)

I believe the answer is:

nil

'nothing' is the definition.
(eg nil is zero in football)

I don't understand the rest of the clue.

(Other definitions for nil that I've seen before include "Zero, zilch" , "Non-existent" , "Score of nought" , "Love" , "Latin zero" .)

I've seen this clue in The Guardian.

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