I recently learnt the word もちきり. It always seems to preceeded by a word with particle で e.g.
Rumours about you are a hot topic at the moment.
I can't understand why で is used. Which type of で is this?
で particle can indicate location of action, time of action, means of action.
で particle also indicates cause of an effect.
In this case, hot topic is the effect of rumors about you. もちきりよ is an effect, and あなたの噂 is a cause.
Hope it helps.