Sign of grief after race, let down (8)
I believe the answer is:
teardrop
'sign of grief' is the definition.
(a grieving person might shed tears)
'after race let down' is the wordplay.
'after' is a charade indicator (letters next to each other).
'race' becomes 'tear' (tearing is a kind of racing).
'let down' becomes 'drop' (to let go of).
'tear' next to 'drop' is 'TEARDROP'.
(Other definitions for teardrop that I've seen before include "spot of grief" , "It falls from the eye" , "Predator (anag.)" , "One shed from eye" , "Parroted (anag.)" .)