The phrase "as a guard for" is correct and usable in written English.
It can be used when describing a protective role or function that something or someone serves for another entity or purpose.
Example: "The security system was installed as a guard for the valuable assets in the building."
Alternatives: "as a protector for" or "as a safeguard for".
He worked as a guard for Nastassja Kinski and then for Arnold Schwarzenegger and Maria Shriver.
He was never assigned to ride in a radio car except as a guard for a corpse.
At 19 Mr. Tuymans encountered a series of El Greco paintings in Budapest while working as a guard for a European railway company.
Muhammad Akram, a 47-year-old father of four playing a local form of draughts, lost his job as a guard for a German NGO two years ago.
Drafted by the Knicks in 1974, he played one season in the N.B.A. as a guard for the Knicks and the Phoenix Suns.
Mr. Bhuiyan said he worked as a guard for Axel Protection Systems in Maspeth, Queens, in 1993, but was let go when the company lost a contract.
Burnham also worked as a cowboy, a guard for the mines, a guide, and a scout during these years.
Daniel Gilroy, who worked alongside Mateen for about a year as a security guard for a gated community, said he brought a prayer rug and skullcap to work and prayed on his knees during his shifts.
The one translator who reported on his Army form that he held a "secret" clearance, Bakeer Naseef, a Jordanian-American, worked as a security guard for a private company before taking the job in Iraq, said his daughter, Siham.
As dropping an ongoing handoff prioritized call is less desired than blocking a new prioritized call arrival, an amount of capacity C is reserved as a guard channel for only handoff prioritized call arrivals.
The 3rd Squadron was detailed as a guard force for the division's artillery, accompanying them to Atawineh.
