Relay perhaps in good time (5)
I believe the answer is:
early
'in good time' is the definition.
(being early is arriving in good time)
'relay perhaps' is the wordplay.
'perhaps' indicates an anagram.
'relay' anagrammed gives 'EARLY'.
(Other definitions for early that I've seen before include "Infancy, when Wordsworth had 5 across of 5 down" , "Premature" , "Untimely" , "before anyone else?" , "Advanced" .)