Corrupt female I left in river (6)
I believe the answer is:
defile
'corrupt' is the definition.
(synonyms)
'female i left in river' is the wordplay.
'female' becomes 'f' (common abbreviation).
'left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'river' becomes 'dee' (River Dee).
'f'+'i'+'l'='fil'
'fil' going within 'dee' is 'DEFILE'.
(Other definitions for defile that I've seen before include "Narrow pass; pollute" , "Desecrate" , "Contaminate" , "dishonour?" , "Mar; narrow gorge" .)