2650: Detention for history

One of the unclued entries is responsible for a quotation that makes up the others (two of three words, one of two words).

Across

1    Precious metals Cook nearly left (1,6)

6    Netball players in mid-court for three quarters? (7)

12    Another one bites the dust, recipe being trapped wind (7)

14    Biting an animal’s brought about this? (5)

15    Married in mostly passionless times (5)

16    Caught this lassie forming a dance party? (6)

17    Top cops needing person to stop suspect (6)

19    Identifiers for Ben and James (minor characters) (9)

21    New ____ could be synthesised by men or women? (7)

24    Farmyard bird made a meal of...