The phrase "a practice which was" is correct and usable in written English.
It can be used when referring to a specific practice that existed or was in effect in the past.
Example: "The study examined a practice which was common in the early 20th century among educators."
Alternatives: "a method that was" or "a technique that was".
Operation Trawler has brought to an end a practice which was once endemic in the British fishing industry, but has been made extremely difficult by hi-tech monitoring and tracking of every registered trawler at sea, and much tighter controls on landings at processing firms.
This is a practice which was commonly used in the coalfields, but is becoming more difficult to practice for both technical and regulatory reasons.
You may recall that in the old days pre-20099), businesses typically used Facebook in one of two ways: either via their personal page (a practice which was later declared 'against the guidelines') or through a Facebook group.
The Broadmoor report found: Savile watched and made inappropriate comments when female patients stripped and showered naked in front of staff, a practice which was common in the late 1980s.
Before that moment, Plato imagines Socrates being visited in prison by his friend Crito (in a dialogue which bears his name), and urged to escape for the sake of his friends and family, a practice which was tolerated in Athens so long as the escapee fled into exile.
Several towns in New York have used zoning ordinances to ban fracking, a practice which was upheld by the state Court of Appeals earlier this year.
Many sharks have their fins cut off before their bodies are thrown overboard, a practice which is meant to be banned under the standards of the Marine Stewardship Council (MSC).
However in an April referendum this year, Maltese voters approved the controversial spring hunting of migratory birds - a practice which is illegal throughout the rest of the EU.
"We cannot tell communities in Sierra Leone and Somalia to stop a practice which is freely permitted on Harley Street," said Keith Vaz, the chairman of the select committee.
Judge Robert E. Payne wrote in a dissenting option that incumbent protection — rather than race — motivated the redistricting, a practice which is legal.
ANNALS OF GOVERNMENT about policing of American writers by the U.S. govt. (principally the F.B.I ., a practice which is apparently continuing.
