Runner of errands accommodating learner — one on course? (6)
I believe the answer is:
golfer
'one on course?' is the definition.
(gofer, l, on course)
'runner of errands accommodating learner' is the wordplay.
'runner of errands' becomes 'gofer' (a gofer does errands for someone).
'accommodating' is an insertion indicator.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'gofer' enclosing 'l' is 'GOLFER'.
(Other definitions for golfer that I've seen before include "Driver, chipper and putter" , "Swinger on course" , "Player on links" , "Player with clubs and tees" , "McGinley or Harrington, say" .)