Reportedly drink something essential on course (3)
I believe the answer is:
tee
'something essential on course' is the definition.
(a tee is used on a golf course)
'reportedly drink' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'drink' becomes 'tea' (tea is a kind of drink).
'tea' is a homophone of 'TEE'.
(Other definitions for tee that I've seen before include "Golf-peg" , "Golfer's starting point" , "Golf ball support" , "Golfing item" , "Part of course" .)