Spoilt odd dream about river (6)
I believe the answer is:
marred
'spoilt' is the definition.
('mar' can be a synonym of 'spoil')
'odd dream about river' is the wordplay.
'odd' indicates anagramming the letters.
'about' is an insertion indicator.
'river' becomes 'r' (abbreviation for river).
'dream' with letters rearranged gives 'mared'.
'mared' enclosing 'r' is 'MARRED'.
(Other definitions for marred that I've seen before include "Blemished" , "'Impaired, spoilt (6)'" , "Damaged or spoiled" .)