Good competition is a blessing (5)
I believe the answer is:
grace
'a blessing' is the definition.
('grace' can be a synonym of 'blessing')
'good competition' is the wordplay.
'good' becomes 'g' (abbreviation).
'competition' becomes 'race' (race is a kind of competition).
'g'+'race'='GRACE'
'is' is the link.
(Other definitions for grace that I've seen before include "beauty of movement" , "Prayer of thanks before/after a meal" , "Elegance of movement" , "Meal blessing" , "Mealtime prayer" .)