When you say locked, it could mean group, blend or combine. If the objects are grouped, you can ungroup them by selecting them and pressing Ctrl/U. I would try this first, and you may have to ungroup a few times.

If some elements are blended together you may not want to release them from the blend, but then again you may, depending on what was released. To release a blend you select it, click the Blend tool (W), and click ‘Remove’. If the objects were combined you can try breaking them apart by selecting them and clicking ‘Arrange’ and ‘Break Shapes’. On the other hand, you might have a combination of grouping and combining, in which case you would ungroup and then break apart. Sometimes blends are blended with other blends, in which case all the blends might need separating and then ungrouping, etc.

So it depends what you actually did with all the objects to ‘lock’ them.

You can sometimes cut out a chunk of the whole group, by simply placing a rectangle (or other shape) over the lot, selecting both and intersecting shapes (Ctrl/3). If this changes things too much, it may be because you had lines or other elements that needed converting first. If so you can try selecting the main collection and converting it to editable shapes (Shift/Ctrl + S), and converting lines to shapes (Arrange/convert Line to Shape), before trying to cut out the section as per above.

So ungroup (maybe a few times), convert to editable shapes and convert lines to editable shapes (if necessary), break apart (if necessary), group all again, place a shape over the section, and try to cut it out.

How did it go?