. . . following behind leader in race (5)
I believe the answer is:
later
'following' is the definition.
(I've seen this in other clues)
'behind leader in race' is the wordplay.
'behind' becomes 'late' (as in behind schedule).
'leader in race' becomes 'r' (I've seen this in other clues).
'late'+'r'='LATER'
(Other definitions for later that I've seen before include "At some time afterwards" , "At a subsequent time" , "at a future date" , "More recent" , "Tomorrow (or next week)?" .)