Rather elderly for such speed? (7)
I believe the answer is:
seventy
This clue might be a double definition.
'rather elderly for' is the first definition.
The definition suggests a singular noun which matches the answer.
'speed?' is the second definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'such' is the link.
Can you help me to learn more?
(Other definitions for seventy that I've seen before include "LXX" , "Threescore and ten" , "A number" , "Three score years and ten" .)