Tie completely round (4,4)
I believe the answer is:
dead heat
'tie' is the definition.
(dead heat is a kind of tie)
'completely round' is the wordplay.
'completely' becomes 'dead' (synonyms).
'round' becomes 'heat' (stage of a competition).
'dead'+'heat'='DEAD-HEAT'
(Other definitions for dead heat that I've seen before include "Race finish with contestants exactly even - or moribund?" , "Racing tie" , "Exactly tied race" , "Equality in finish of race" , "A draw in race, competitors finish exactly even" .)