Highfliers get good scores on the course (6)
I believe the answer is:
eagles
'scores on the course' is the definition.
'eagles' can be an answer for 'scores' (eagle is a kind of score). I'm unsure of the 'on the course' bit.
'highfliers get good' is the wordplay.
'highfliers' becomes 'eales' (I can't explain this - if you can you should give a lot more credence to this answer).
'get' is an insertion indicator.
'good' becomes 'g' (abbreviation).
'eales' placed around 'g' is 'EAGLES'.
Can you help me to learn more?
(Other definitions for eagles that I've seen before include "Such raptors" , "Soaring birds of prey (6)" , "They nest in eyries" , "Golf scores of two under par" , "Below-par" .)