Some mess often swirling around in ditch (5)
I believe the answer is:
fosse
'ditch' is the definition.
(fosse is a kind of ditch)
'some mess often swirling around' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'around' says the letters should be written backwards.
'essof' can be found hidden inside 'mess often swirling'.
'essof' back-to-front is 'FOSSE'.
'in' acts as a link.
(Other definitions for fosse that I've seen before include "Fortification ditch" , "Ditch or moat" , "Long, narrow trench or excavation" , "Long narrow ditch" , "Long trench or ditch" .)