Simple answer is no. Terms of reference cannot override legislation and legislation states that any meeting of the council or any committee thereof must be open to the public, must have an agenda which must be published no later than three clear days before the meeting, etc. etc. Even if the usual business of that committee would fall within the acceptable reasons for excluding the public, the public (and council members!) are still entitled to be told, to view the agenda and to attend, if they so wish, to hear apologies, declarations of interest etc. and the agreement of the minutes of the previous meeting which, incidentally, are not confidential either. The discussion can be without the public present, assuming the relevant resolution to exclude the public is agreed (and the reason for exclusion is appropriate and in accordance with legislation) but any resolution is not confidential albeit that it can be worded rather vaguely.
For the record, a task and finish group or working group can be formed which doesn't need any of the formalities mentioned such as being open to the public, but such groups can never have delegated authority to make decisions. They are usually used for fact finding type sessions which they bring their ideas or recommendations to a suitably authorised committee or full council.