Whereon the first or last of the skiers moves easily (6)
I believe the answer is:
slopes
'whereon the first' is the definition.
I can't tell whether this definition defines the answer.
'last of the skiers moves easily' is the wordplay.
'last of' says to take the final letters.
'moves easily' becomes 'lopes' (I've seen this in another clue).
The last letter of 'skiers' is 's'.
's'+'lopes'='SLOPES'
'or' is the link.
Can you help me to learn more?
(Other definitions for slopes that I've seen before include "Of fairly great stature" , "Stretches of falling ground as for skiers" , "Gradients, inclines" , "Slanting surfaces" , "Inclines, pitches" .)