The usual phrase is "go the extra mile", and its meaning is discussed in this thread: go the extra mile.
We need more information to tell you why 'yard' was substituted for 'mile' in the phrase you saw. Please tell us where you saw this phrase. Give us the complete sentence. What was being discussed? And so on. It is some kind of play on words, and we need context to explain it, which is what we would like to do.
hello, Cagey, many thanks for your explanation, I came across the phrase "go the extra" yard while reading a journalist's CV:
The ‘go the extra’ yard approach, included scrapes with danger such as the occasion where she talked her way onto a military helicopter to report from the centre of the Somali conflict in the early 1990’s at the height of the political crisis and the ensuing famine that followed the ouster of the then Somali President Siad Barre.
I have never heard it, but I see on the internet that "go the extra yard" is indeed used with a meaning similar to 'go the extra mile', that is: "to do something in addition to what is required, to do something very completely."
I suspect it may be a combination of 'go the extra mile' with another idiom:
go the whole nine yards (American informal)
to continue doing something dangerous or difficult until it is finished
To my knowledge, "go the extra yard" is not regular idiom, but combines the ideas behind 'go the extra mile' and 'go the whole nine yards': The reporter did more than one would expect or than her job absolutely required in order to report on events in dangerous places.
(Would you please give the name of the source as well? It's something we require for every quotation.)