Sports contest initially banned in most of Leinster town (8)
I believe the answer is:
biathlon
'sports contest' is the definition.
'initially banned in most of leinster town' is the wordplay.
'initially' says to take the initial letters.
'most of' means to remove the last letter.
'leinster town' becomes 'athlone'.
The first letters of 'banned in' is 'bi'.
'athlone' with its final letter taken off is 'athlon'.
'bi'+'athlon'='BIATHLON'
(Other definitions for biathlon that I've seen before include "Winter sport involving rifles" , "Contest in two sporting disciplines, say cycling and running" , "Sporting event of rifle shooting and cross-country skiing" , "Cross-country skiing/rifle shooting sports event" , "winter sports event" .)