Sign of trail-bike ruts Egyptologist's covered over (7)
I believe the answer is:
gesture
'sign' is the definition.
(gesture is a kind of sign)
'trail-bike ruts egyptologist's covered over' is the wordplay.
'covered' indicates a hidden word (the answer is covered up by the clue).
'over' says the letters should be written in reverse.
'erutseg' can be found hidden inside 'trail bike ruts egyptologist'.
'erutseg' backwards is 'GESTURE'.
'of' acts as a link.
(Other definitions for gesture that I've seen before include "wave, perhaps?" , "Hand movement to communicate" , "Significant movement" , "A physical motion or signal" , "Movement, indication" .)