There are two components to this phrase to break down.
- [for someone] to do what one is expected to do, especially under difficult conditions
With regards to in the clutch, we have to look at the definition of clutch. In this context, Darry is using it in the same way it is often used in sports. In sports it is often used to describe players who can make the best plays even when the pressure is highest. For a person to be good in the clutch means to be able to perform in those critical moments, regardless of the pressure or stakes riding on the outcome of the game or match they're participating in.
So just taking in the clutch on its own, it means those moments where the stakes and the pressure are at their highest.
Combining these two definitions, to be coming through in the clutch means that Trisha has followed through and helped Darry, right when he needed it most.
However, before Darry says this, Trisha drops him when they're confronted by rats. This is the opposite of being clutch, so Darry is likely being sarcastic in his comment, saying that Trisha choked under pressure.