Truth about groove (3)
I believe the answer is:
'groove' is the definition.
(I know that groove can be written as rut)
'truth about' is the wordplay.
'about' indicates the answer is hidden within the clue (the clue goes around or about the answer).
'RUT' is hidden within 'truth'.
(Other definitions for rut that I've seen before include "Deep groove as in a lane" , "Groove worn by wheels" , "Well-worn track" , "A deep track - get out of it" , "Deep worn track, a bad place to be" .)