In 1971, at age 36, Clemente had 1.8 defensive WAR in 1,081 innings (about 120 games).
In 1972, he had 1.0 defensive WAR in 812 innings (about 90 games).
Only two other players had at least 0.8. Robin Yount had 0.9 in 1993 at age 37. Steve Finley had 0.8 in 2004 at age 39.
If we lower the minimum defensive WAR to 0.5, it was done only 12 times outside of Clemente and only one guy did it more than once, Finley. Finley had 0.6 in 2001 at age 36.
Lonnie Smith had 0.7 at age 36 in 1992 but in only 84 games. Pretty impressive. Stan Javier had 0.8 at age 37 in 2001 in 89 games (he shows up if I set a minimum of 0.75 but not at 0.8).
If we lower the age to 35 but go back to a minimum of 1.0, there are still only 4 cases outside of Clemente. Here they are:
If we look at ages 36-37 combined, Clemente has 2.7 (there must be a rounding issue because it is not 2.8). The only other guy with at least 1.0 is Finley, at 1.0.