Absurd eulogy mostly describing a river dip (9)
I believe the answer is:
guacamole
'dip' is the definition.
(I know that guacamole is a type of dip)
'absurd eulogy mostly describing a river' is the wordplay.
'absurd' indicates an anagram.
'mostly' means to remove the last letter (most but not all of the word).
'describing' means one lot of letters goes inside another (describe can mean to form the outline of).
'river' becomes 'cam' (river in Cambridge, England).
'eulogy' with its final letter taken away is 'eulog'.
'eulog' is an anagram of 'guole'.
'a'+'cam'='acam'
'guole' enclosing 'acam' is 'GUACAMOLE'.
(Other definitions for guacamole that I've seen before include "Avocado dip" , "Mashed avocado dish" , "tasty dip" , "Mexican dish" , "Avocado-based dish" .)