Hi Ann
Thanks for explaining the areas, the Barony area has always had me baffled.
As you might realise, I have been going through these quite quickly, and it is getting late!, but still nobody has come up as born in Nitshill. Nonetheless, SDGW does not necessarily give the birthplace. It might only state where a man
enlisted which can be annoying but I suppose it is what the man 'gave out' or volunteered to the recruiter, when he enlisted or was 'called up'.
So! I thought the William Orr rellie was going to be more promising for you. However, now that you seem definite about Nitshill area, I am no longer hopeful. Still, just incase here is a couple from the Renfrewshire area:
William Orr, Pte 1392, 1st (Royal) Dragoons died 12/11/1914 so would only have been 14 years old
on Panel 5 at Ypres. He was born Greenock, Renfrewshire.
William Orr, (born Glasgow, enlisted Glasgow, residence Greenock).
Pte 3944, 3rd (Reserve) Bn HLI
Died 10/06/1915. It states he died at home, but that could mean in Scotland as he is buried at Comely Bank, Edinburgh amongst the military graves.
There is also a William Orr of Newton Mearns, and another from Bridgeton and yet another from Milngavie. But, not exactly what you are looking for!

The latter was aged 32 when killed, so can rule him out, but very often the age is not mentioned.