It's the custom to give us time (5)
I believe the answer is:
usage
'it's the custom' is the definition.
(synonyms)
'give us time' is the wordplay.
'give' says to put letters next to each other.
'time' becomes 'age' (an age is a period of time).
'us' next to 'age' is 'USAGE'.
'to' acts as a link.
(Other definitions for usage that I've seen before include "Custom - treatment" , "Habit" , "Established custom" , "Terminology - custom" , "management" .)