The kind of crust found only on the best pies? (5)
I believe the answer is:
upper
'the kind of crust' is the definition.
(I've seen this in another clue)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for upper that I've seen before include "Higher; part of boot" , "The higher of two, berths perhaps" , "catcher of swans?" , "form of stimulant" , "Part of shoe above sole" .)