Water flowing badly, river choked by spicy stuff (8)
I believe the answer is:
millrace
'water flowing' is the definition.
(current powering a mill)
'badly river choked by spicy stuff' is the wordplay.
'badly' becomes 'ill' ('ill' can be adverbial as in 'ill-advised').
'river' becomes 'r'.
'choked by' means one lot of letters goes inside another (I've seen this in other clues).
'spicy stuff' becomes 'mace'.
'ill'+'r'='illr'
'illr' inserted within 'mace' is 'MILLRACE'.
(Other definitions for millrace that I've seen before include "current providing power" , "Channel for water driving wheel" , "Channel leading to water wheel" , "Flow of water" , "Channel for the water current that turns a wheel" .)