The phrase "a lot of time and effort" means that someone has put in a significant amount of work or spent a considerable amount of time on something. Full definition
You should be prepared to put lots of time and effort into it, and try to avoid being discouraged if you are rejected a few times along the way. (articlesfactory.com)
Open houses take lots of time and effort, so build anticipation with an event page and invite. (placester.com)
These two groups spent lots of time and effort defending their methods and attacking those of the opposing camp. (trainingscience.net)