Comment by FearNotDaniel

Ah, the unintentional ambiguity of language, the reason there are so many lawyers in the world and why they are so expensive. The GP's phrasing is not incorrect but your comment made me realize: I only parsed it correctly the first time because I've heard managers use similar phrases so I recognized the metaphor immediately. But for the sake of reducing miscommunication, which sadly tends to trigger so many conflicts, I could offer a couple of disambiguatory alternatives:

- "her job was to be a crap-umbrella": hyphenate into a compound noun, implies "an umbrella of/for crap" to clarify the intended meaning

- "her job was to be a crappy umbrella": make the adjective explicit if the intention was instead to describe an umbrella that doesn't work well