If your drawings are showing frames around blocks and clipped xrefs
and you need to remove it try

FRAME = 0

AutoCAD Help says:

Turns the display of frames on and off for all external references, images, and DWF, DWFx, PDF, and DGN underlays. The FRAME setting overrides the individual IMAGEFRAME, DWFFRAME, PDFFRAME, DGNFRAME, and XCLIPFRAME settings.
0 The frame is not visible and it is not plotted

1 Displays the frame and allows it to be plotted

2 Displays the frame but keeps it from being plotted

3 The setting varies for all attached images, underlays, and xrefs

or another solution

The possible reason: It’s come from any regular block or dynamic block after they got xclipped. In 2000 – 2010 versions the xclip frame is invisible and uneditable but from 2011 you can set it visibility via the XCLIPFRAME variable and grip edit / invert it.

XCLIPFRAME = 0 to turn off.

That’s a clip boundary. The benefit of leaving it on is that you can edit the clip from the boundary grips, and invert clipping side (likes making a hole inside your block, in your case, the boundary is larger than the block extent so when you invert it, you see nothing).

or

FRAMESELECTION (System Variable)

Set FRAMESELECTION to 0

Controls whether the hidden frame of an image, underlay, clipped xref, or wipeout can be selected.

Type: Integer
Saved in: Registry
Initial value: 1

Value

Description

0
Hidden frames cannot be selected
1
Hidden frames can be selected.