50% of nepotism's flipping obvious (4)
I believe the answer is:
open
'obvious' is the definition.
(similar in meaning)
'50% of nepotism's flipping' is the wordplay.
'50% of' means to take half the letters.
'flipping' is a reversal indicator.
'nepotism' halved is 'nepo'.
'nepo' backwards is 'OPEN'.
(Other definitions for open that I've seen before include "Candid - ready for business" , "sporting competition" , "Not closed or obstructed" , "unsealed" , "This championship includes both professional and amateur golfers" .)