Catch up in an hour (3)
I believe the answer is:
ten
This clue could be a double definition.
'catch up' is the first definition.
(I've seen this in other clues)
'an hour' is the second definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'in' is the link.
Can you help me to learn more?
(Other definitions for ten that I've seen before include "Cardinal number" , "Very young" , "Half a score" , "Roman numeral X" , "time" .)