Furrow of truth (3)
I believe the answer is:
rut
'furrow' is the definition.
(I know that furrow can be written as rut)
'of truth' is the wordplay.
'of' indicates a hidden word.
'RUT' can be found hidden inside 'truth'.
(Other definitions for rut that I've seen before include "Groove worn by wheels" , "It can be frustrating" , "Deep track worn as by wheel" , "Kind of groove or fixed habit" , "have sex!" .)