Climber close to insanity following strange vision on river (6,3)
I believe the answer is:
poison ivy
'climber' is the definition.
(I've seen this before)
'close to insanity following strange vision on river' is the wordplay.
'close to' says to put letters next to each other.
'insanity following' becomes 'y' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'strange' is an anagram indicator.
'on' is an insertion indicator (as in clothing 'on' a person).
'river' becomes 'Po' (Italian river).
'vision' anagrammed gives 'isoniv'.
'isoniv' going around 'po' is 'poisoniv'.
'y' put after 'poisoniv' is 'POISON-IVY'.
Can you help me to learn more?
(Other definitions for poison ivy that I've seen before include "North American toxic plant" , "American climbing plant that causes dermatitis on contact - 1992 film with Drew Barrymore" , "climber" .)