Truth about groove (3)
I believe the answer is:
rut
'groove' is the definition.
(I know that groove can be written as rut)
'truth about' is the wordplay.
'about' indicates a hidden word (the clue goes around or about the answer).
'RUT' can be found hidden inside '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" .)