Good score, for a flyer (5)
I believe the answer is:
eagle
This clue is a double definition.
'good score' is the first definition.
(I've seen this before)
'a flyer' is the second definition.
(I've seen this before)
'for' is the link.
(Other definitions for eagle that I've seen before include "Score of two strokes under par for a golf hole" , "part of round that's exceptional" , "high-flier" , "drugs with silver left inside" , "Keen-eyed bird" .)