Literal translation
to do a good turn, a good favor
Meaning
to do someone a good turn, a friendly gesture
Explanation
In its plain sense it means doing a favour, a friendly gesture, directly tied to the word maniero, close to the French manière. A second, frankly erotic meaning overlays it : performing oral sex. The shift makes sense as a wink at easy gallantry, treating the act as a form of generous welcome. Best to read the context carefully before using the phrase, or risk an awkward misunderstanding.