Streak on a cheek (4)
I believe the answer is:
tear
'streak on a cheek' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tear that I've seen before include "Rent - drop" , "Small flaw, as in glass" , "charge" , "Lachrymal fluid" , "A rip or cut" .)