Catch up in time (3)
I believe the answer is:
ten
This clue is a double definition.
'catch up' is the first definition.
(I've seen this in other clues)
'time' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for ten that I've seen before include "Cardinal number" , "Base of decimal system" , "X-WORD" , "No of sides of a decagon" , "PM's address, Downing St" .)