You would use the read function, however, since the DXF data has been converted to a string, the entity name pointers (e.g. <Entity name: 7ef08940>) will no longer be accessible and will cause the read function to error since they will be interpreted as two separate symbols which form an invalid dotted pair structure.
For example, the dotted pairs containing entity names would be equivalent to attempting to convert:
$ (read "((-1 . a b))")
; error: extra cdrs in dotted pair on input
Since the two parts of the entity name pointer would be interpreted as two individual symbols:
(-1 . <Entity name: 7ef08940>)
And a dotted pair may only consist of two atoms, no more, no less.