Relative pronoun "ἅ"

[Asterisk1234]

I'm on unit 21 in M.; Exercise I.7 (p.179) is to translate the sentence " ἅ μεθ' ὕΒρεως αὐτοι πράττομεν, etc. ". The answer key gives "What we ourselves do with insolence..". As far as I know from unit 8, " ἅ " is a relative pronoun neuter plural nominative or accusative meaning "that", with an antecedent e.g.: "the mistakes that I make..." How can it be translated as "What...", which I would define in this case as an indefinite pronoun.

Thanks to all.

[Constantinus Philo]

that which we do with insolence..... antecedent omitted.

[wilberfloss]

a = 'the things which'.
In the same way, for example, the masc. nom. pl. of the relative pronoun can be translated as 'the men who', etc.