No elm can produce fruit! (5)
I believe the answer is:
lemon
'fruit' is the definition.
(I know that lemon is a type of citrus fruit)
'no elm can produce' is the wordplay.
'can produce' indicates anagramming the letters (I've seen this in other clues).
'no'+'elm'='noelm'
'noelm' is an anagram of 'LEMON'.
(Other definitions for lemon that I've seen before include "A fruit; a worthless item" , "Shade of yellow - fruit" , "failure" , "stinker" , "certainly not a plum!" .)