Apex domains cannot have CNAME records.
Question and response
Question
dig ds.strath.ac.uk. NS
Answer
ds.strath.ac.uk. 5 NS its-dc5.ds.strath.ac.uk.
ds.strath.ac.uk. 5 NS its-dc6.ds.strath.ac.uk.
ds.strath.ac.uk. 5 NS its-dc4.ds.strath.ac.uk.
Authority
The response has no authority records.
Additional
its-dc4.ds.strath.ac.uk. 5 A 130.159.17.140
its-dc5.ds.strath.ac.uk. 5 A 130.159.18.112
its-dc6.ds.strath.ac.uk. 5 A 130.159.250.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0