Filth of river: one lifted dog out of water (8)
I believe the answer is:
ribaldry
'filth' is the definition.
(filthy or indecent speech or behaviour)
'river one lifted dog out of water' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'one' becomes 'i' (Roman numeral).
'lifted' is a reversal indicator (going up in down clue).
'dog' becomes 'lab' (short for labrador).
'out of water' becomes 'dry' (as opposed to wet).
'lab' in reverse letter order is 'bal'.
'r'+'i'+'bal'+'dry'='RIBALDRY'
'of' acts as a link.
(Other definitions for ribaldry that I've seen before include "unseemly mirth" , "Vulgar and disrespectful humour" , "Obscene language" , "Behaviour or language bordering on indelicacy" , "Rabelaisian behaviour" .)