High jumper rocks during walk (4,4)
I believe the answer is:
tree frog
'high jumper' is the definition.
(I've seen this before)
'rocks during walk' is the wordplay.
'rocks' becomes 'reef' (I've seen this before).
'during' indicates putting letters inside.
'walk' becomes 'trog' (I can't justify this - if you can you should give a lot more credence to this answer).
'reef' placed inside 'trog' is 'TREE-FROG'.
Can you help me to learn more?
(Other definitions for tree frog that I've seen before include "Arboreal amphibian" , "Amphibian found in the branches?" , "High jumper" .)