> I will have a discrete word them.
Is not grammatical. You can have a word _with_ them.

**Discrete** here means _using discretion_, respecting issues of privacy and decency.

Having a word with someone means having a talk with them.

Having a _discreet_ word with someone usually means you talk to someone in private - you take them apart at the coffee corner, or you move into a meeting room. It indicates the _opposite_ of giving someone a public telling off.
It is often considered unkind to criticize someone in public, in front of their friends or colleagues. Having a _discrete_ word with them, you make sure they do get the message,but it is not a public event.