Wanting best position in race run round (7)
I believe the answer is:
elitism
'wanting best' is the definition.
'position in race run round' is the wordplay.
'position' becomes 'sit' (sitting is a kind of positioning).
'in' is an insertion indicator.
'race' becomes 'mile'.
'run round' is a reversal indicator.
'sit' placed within 'mile' is 'msitile'.
'msitile' backwards is 'ELITISM'.
(Other definitions for elitism that I've seen before include "Exclusive attitude" , "lapping up the cream" , "goverment by chosen group" , "favouring the top people" , "Belief in the best" .)