Unfortunately no elm tree (5)
I believe the answer is:
'tree' is the definition.
(lemon is a kind of tree)
'unfortunately no elm' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'noelm' anagrammed gives 'LEMON'.
(Other definitions for lemon that I've seen before include "Fruit; sort of grass, sole" , "Fruit-tree" , "definitely not a peach" , "Unhelpful answer" , "Fruit high in vitamin C" .)