The phrase "intensive work" refers to a task or job that requires a lot of effort, focus, and concentration.
Sentences with «intensive work»
It's important to recognise that any form of intensive work with clients can be emotionally demanding. (prospects.ac.uk)
Additionally, While You're Away can be a great option for dogs who may need more intensive work on a behavioral issue than single private training sessions have to offer. (acanineaffinity.com)
That's an area that I've done intensive work in. (lawyerist.com)