Most of the view on river is declining as the years go by (6)
I believe the answer is:
senile
'declining as the years go by' is the definition.
I can't judge whether this definition defines the answer.
'most of the view on river' is the wordplay.
'most of' means to remove the last letter.
'the view' becomes 'see' (I've seen this before).
'on' says to put letters next to each other.
'river' becomes 'nile' (Nile is an example**).
'see' with its final letter removed is 'se'.
'se'+'nile'='SENILE'
'is' is the link.
Can you help me to learn more?
(Other definitions for senile that I've seen before include "Old and infirm" , "In one's dotage" , "Doddering" , "Mentally infirm with age" , "Suffering from mental weakness due to old age" .)