41 pledged delegates are at stake in Iowa.
I'm going to summarize the US primary system very broadly, since it's not really the point of the question, but it does help to have some understanding of it for context. Most of this is adapted from Wikipedia if you want to read more in depth.
Throughout the primaries (the process to select a presidential nominee for a political party), each state has a certain number of delegates assigned to it, proportional to how many people are in the state. There are 4765 Democratic delegates nation-wide, and a candidate must win 1990 of them to become the Democratic Party presidential nominee.
In each state's primary or caucus, the citizens choose which candidate they want their state to award delegates to. States have different rules on how this works - some states are "winner-take-all", where the candidate who wins the majority vote gets all of the state's delegates, and some states divide them up proportionally by the votes.
In Iowa, the process of a caucus is more complicated than just a ballot vote, but the state has 41 delegates, and they are awarded proportionally to the candidates that get the most support.
So "at stake" in this context means "to be won or lost", as in the stakes of a game or competition. (source, under the "Phrases" heading of stake2.) 41 delegates may be won by the candidates.
"At stake" is defined as "at risk" or "in question", so it doesn't necessarily mean life-threatening jeopardy - it just puts them at risk of losing something within the context under discussion.
So your definition is broadly correct. These delegates are "at risk" of not being selected for office.
Being British, I don't fully understand American politics, but I believe that delegates are first put forward to run for office by local members of a political party. It is only if they perform well in this first contest that they can then go on to secure the nomination. So they are "at risk" as delegates, meaning their political office is still in doubt, until they are nominated.