The German word »wenig« is not an adverb, it is an adjective. The main difference between adverbs and adjectives is, that adverbs only can be used in adverbial usage, while adjectives can be used adverbial, predicative and as an attribute.
- adverbial usage
- adjective
Die Frau singt schön. The woman sings beautifully.
- adverb
Die Frau singt oft. The woman sings often.
- predicative usage
- adjective
Die Frau ist schön. The woman is beautiful.
- adverb
wrong: Die Frau ist oft. The woman is often.
- attributive usage
- adjective
Die schöne Frau singt. The beautiful woman sings.
- adverb
wrong: Die ofte Frau singt. The often woman sings.
In your sentence the word »weniger« is used as an attribute, so it can't be an adverb. It must be an adjective.
Adjectives can describe properties of nouns:
Das leise Instrument hat einen schönen Klang.
Das wenige Essen war sehr teuer.
Adjectives can describe properties of participles:
Der leise sprechende Mann war blass.
Die wenig essende Frau schlief etwas später ein.
Adjectives can describe properties of adverbs:
Hoch oben auf den Bergen liegt schon Schnee.
Die beiden Orte liegen nur wenig auseinander.
But adjectives also can describe properties of other adjectives:
Der grell rote Ball lag in der Wiese.
Man muss ab und zu auch mal eine wenig gerechte Aufgabenteilung im Beruf hinnehmen.
Note, that in the last two examples the bold marked adjectives do not describe a property of the noun, but a property of the adjective that stands immediately after them.
Also note, that adjectives, that are attributes of other adjectives, are not inflected, since they do not belong to a noun. Only adjectives that are attributes of nouns will be inflected.
Compare:
- Der grell rote Ball lag in der Wiese.
- Der grelle rote Ball lag in der Wiese.
In 1 the word grell (glaring) describes a property of the adjective rot (red).
In 2 the word grelle describes a property of the noun Ball (ball).
Since in English adjectives never are inflected, both German sentences translate to the same English sentence, but in the English sentence it is ambiguous if the adjective glaring is bound to red or to ball:
The glaring red ball lay in the meadow.
This can mean:
- attribute of an adjective: The ball, that is glaring red, lay in the meadow.
- attribute of a noun: The glaring and red ball lay in the meadow.
And, like many adjectives (but almost no adverb), the adjective »wenig« not only exists in its positive form, but also in a comparative and a superlative form:
- positiv: wenig (Engl: little)
- comparative: weniger (less)
- superlative: am wenigsten (least)
And in your sentence it is used in the comparative form:
Man muss ab und zu auch mal eine weniger gerechte Aufgabenteilung im Beruf hinnehmen.
From time to time one has to accept a less fair division of tasks in one's job.
Also in the english translation the adjective little in its comparative form less does not describe a property of the noun division. The adjective less describes a property of the adjective fair.