I’m going round part of farmyard in a fog (5)
I believe the answer is:
misty
'in a fog' is the definition.
(thesaurus)
'i'm going round part of farmyard' is the wordplay.
'going round' shows that the letters should be reversed in order.
'part of farmyard' becomes 'sty' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'im' backwards is 'mi'.
'mi'+'sty'='MISTY'
Can you help me to learn more?
(Other definitions for misty that I've seen before include "Cloudy, foggy" , "Dim, obscure, clouded" , "Dim, indistinct" , "Indistinct; slightly foggy" , "Indistinct in outline" .)