一身本领, 一团和气: number + measure word + abstract noun

A number (almost always 一) + a figurative measure word + an abstract noun presents a quality, a feeling or an ability as an amount that fills everything: 一身本领 (a whole range of skills), 一团和气 (an atmosphere of goodwill). The measure word is not the all-purpose 个: it is borrowed from a part of the body or from a shape, and it supplies the image. 身 is the whole body ("from head to toe"), 脸 the face (what shows on it), 肚子 the belly (what weighs on the heart), 团 a ball or compact mass, 股 a thread that rises or spreads.

The sense taught here. The standard's entry (数词 + 量词 + 抽象事物) gives 一身本领 and 一团和气 as its examples. This page teaches that mould and adds only groups built the same way and common in narration: 一身疲惫, 一脸严肃, 一肚子委屈, 一股暖意. Each measure word is tied to its noun, so you learn the group as a unit, like an idiom.

The group follows 有 (他有一身本领) or serves by itself as a predicate or a manner adverbial (他一脸严肃地看着我). It is a written, literary device, more vivid than 有 + 个 + noun (有一个想法); in everyday speech you would more likely say 很累 or 很严肃.