Record those signing up for competition (5)
I believe the answer is:
entry
This clue is a double definition.
'record' is the first definition.
(entry is a kind of record)
'those signing up for competition' is the second definition.
(all those who have entered a competition)
(Other definitions for entry that I've seen before include "Debut" , "List of competitors" , "Lobby" , "Competitor" , "candidate" .)