Informed old coin is found in river to the west (8)
I believe the answer is:
educated
'informed' is the definition.
(similar in meaning)
'old coin is found in river to the west' is the wordplay.
'old coin' becomes 'ducat' (I've seen this before).
'is found in' means one lot of letters goes inside another.
'river' becomes 'Dee' (River Dee).
'to the west' says the letters should be written in reverse (letters written right to left or 'east to west').
'dee' written backwards gives 'eed'.
'ducat' going inside 'eed' is 'EDUCATED'.
(Other definitions for educated that I've seen before include "Clever" , "Maybe enlightened" , "Trained; learned" , "Schooled, enlightened" , "Well-read" .)