Enthusiastic patron of local obstacle race (6)
I believe the answer is:
barfly
'enthusiastic patron of local' is the definition.
(barfly can mean someone who drinks in a bar)
'obstacle race' is the wordplay.
'obstacle' becomes 'bar' (bar can mean an obstacle or blockage).
'race' becomes 'fly' (I've seen this in other clues).
'bar'+'fly'='BARFLY'
(Other definitions for barfly that I've seen before include "pub regular" , "frequenter of pubs" .)