circumlocution

A roundabout or indirect way of speaking; thus

Unnecessary use of extra words to express an idea, such as a pleonastic phrase (sometimes driven by an attempt at emphatic clarity) or a wordy substitution (the latter driven by euphemistic intent, pedagogic intent, or sometimes loquaciousness alone).

Necessary use of a phrase to circumvent either a vocabulary fault (of speaker or listener) or a lexical gap, either monolingually or in translation.

An instance of such usage; a roundabout expression, whether an inadvisable one or a necessary one.