Watercourses caught smells (6)
I believe the answer is:
creeks
'watercourses' is the definition.
(creek is a kind of watercourse)
'caught smells' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'smells' becomes 'reeks' (reek is a kind of smell).
'c'+'reeks'='CREEKS'
(Other definitions for creeks that I've seen before include "Small streams in the US" , "Small natural streams of water" , "Watercourses" .)