Highest old tree Frenchman cuts (7)
I believe the answer is:
extreme
'highest' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for extreme that I've seen before include "Going to great lengths" , "Of the greatest intensity" , "too much" , "Acute, maximum" , "Unrestrained" .)