Translation:A Klingon warrior is always willing to fight for the empire.
Klingon grammar doesn't really have "adjectives". There are verbs that can be used in an adjectival fashion and nouns that can be used in an adjectival fashion. When a "be" verb follows a noun in Klingon it is acting as an adjective on that noun. But when two verbs appear next to each other with no markers on the first one to indicate its role, then the first noun is describing the second noun. Such a noun-noun pair may be describing ownership, possession, physical material, origination, or organizational class. You have already experienced this type of noun-noun possession in the phrase tlhIngan Hol which, depending on context might be translated as: "the Klingon's language," "a Klingon language," "Klingon language," "a language of the Klingon," "the language of Klingons," etc. A SuvwI' tlhIngan would be "a warrior type of Klingon". In this case we intentionally used tlhIngan SuvwI' "a Klingon type of warrior."
tlhIngan is a noun, not an adjective.
This is a noun modifying another noun, a bit like (say) "eye drops" in English, where we don't use an adjective (say, "ocular") but use a noun "eye" to modify another noun "drops".
A tlhIngan SuvwI' is not a warrior who is Klingon (adjective) but a warrior who is a Klingon (noun).
No audio has been added, at all, to these later skills. But I'm guessing what you mean is that Duolingo gave you a listening exercise for this sentence even though there is no audio on this sentence, right? Are you using Android? And have you been able to hear any of the audio at all on the Android.