Refer to eccentric golfer’s top: an impressive jumper! (4,4)
I believe the answer is:
tree frog
'an impressive jumper' is the definition.
(frog which can jump very high)
'refer to eccentric golfer's top' is the wordplay.
'eccentric' indicates an anagram.
'top' suggests taking the first letters.
The first letter of 'golfers' is 'g'.
'refer'+'to'='referto'
'referto' with letters rearranged gives 'treefro'.
'treefro'+'g'='TREE FROG'
(Other definitions for tree frog that I've seen before include "Amphibian found in the branches?" , "High jumper" , "Arboreal amphibian" .)