Tree fruit’s ace crop (5)
I believe the answer is:
acorn
'tree fruit's' is the definition.
'acorn' can be an answer for 'fruit's' (acorn is a kind of fruit). I am not sure about the 'tree' bit.
'ace crop' is the wordplay.
'ace' becomes 'a' (abbreviation).
'crop' becomes 'corn' (a farmer's crop of corn).
'a'+'corn'='ACORN'
Can you help me to learn more?
(Other definitions for acorn that I've seen before include "Fruit-seed of the oak" , "Nut of oak tree" , "Fruit of the oak tree" , "Source of a great oak" , "oak's fruit" .)