Is it ok to have creatinine clearance of 42 at 92 ?

Almost normal: It is normal to lose some filtering units with age so that after age 40 the creatinine clearance starts to fall. This will be accelerated by hypertension or obesity or diabetes but even in normal individuals it falls at a lower rate. At age 90 a creatinine clearance of about 60 mls per min would be expected so 42 is close to it.

Yes: Kidney function tapers off as we get into old age. This is just a little less than the healthiest folks can expect. Be glad the kidneys are adequate.