Finish tidily, part of competition being cancelled (5,3)
I believe the answer is:
round off
'finish tidily' is the definition.
(to round something off is to finish it off neatly)
'part of competition being cancelled' is the wordplay.
'part of competition' becomes 'round' (as in a round in a contest).
'being cancelled' becomes 'off' ('off' can be similar in meaning to 'cancelled').
'round'+'off'='ROUND OFF'
(Other definitions for round off that I've seen before include "Conclude" , "finish" .)