Tart relative (3)
I believe the answer is:
pie
'tart relative' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pie that I've seen before include "Very easy answer as" , "Pecan or blueberry dish?" , "Covered tart" , "Irrational things to do with circles and logs" , "Slapstick missile" .)