50 entering contest in total (8)
I believe the answer is:
complete
'total' is the definition.
(similar in meaning)
'50 entering contest' is the wordplay.
'50' becomes 'l' (Roman numeral).
'entering' means one lot of letters goes inside another.
'contest' becomes 'compete' (I've seen this before).
'l' going within 'compete' is 'COMPLETE'.
'in' acts as a link.
(Other definitions for complete that I've seen before include "Finished, entire" , "Full" , "Perfect - finish" , "accomplished" , "whole,entire,uncut" .)