Leading Australian tried to dodge rule (5)
I believe the answer is:
ahead
'leading' is the definition.
(to lead is to go ahead)
'australian tried to dodge rule' is the wordplay.
'australian' becomes 'A' (common abbreviation).
'tried' becomes 'heard' (as in trying or hearing in a trial).
'to dodge' is a deletion indicator.
'rule' becomes 'r' (legal abbreviation).
'heard' with 'r' removed is 'head'.
'a'+'head'='AHEAD'
(Other definitions for ahead that I've seen before include "likely to win?" , "In front as in race" , "In the lead, in advance" , "Forward - in front" , "at pole" .)