Counteract a spread of stale urine (10)
I believe the answer is:
neutralise
'counteract' is the definition.
(I've seen this before)
'a spread of stale urine' is the wordplay.
'a spread of' indicates anagramming the letters (I've seen this in other clues).
'stale'+'urine'='staleurine'
'staleurine' with letters rearranged gives 'NEUTRALISE'.
(Other definitions for neutralise that I've seen before include "offset" , "Counteract" .)