Ultimate height of a river that amazes me (6)
I believe the answer is:
apogee
'ultimate height' is the definition.
'apogee' can be an answer for 'height' (I have seen 'highest height' mean 'apogee' so perhaps 'height' could also mean 'apogee'). I'm unsure of the 'ultimate' bit.
'a river that amazes me' is the wordplay.
'river' becomes 'po' (Italian river).
'that amazes me' becomes 'gee' (I can't justify this - if you can you should give a lot more credence to this answer).
'a'+'po'+'gee'='APOGEE'
'of' is the link.
Can you help me to learn more?
(Other definitions for apogee that I've seen before include "Apex, peak" , "Point in the orbit of the moon that's furthest from the earth" , "highest height" , "(Orbit) most distant point from earth" , "Highest point (of orbit)" .)