Plant cherry to the left beside acorn, I gathered (9)
I believe the answer is:
coriander
'plant' is the definition.
(coriander plant is a kind of plant)
'cherry to the left beside acorn i gathered' is the wordplay.
'cherry' becomes 'red' (synonyms).
'to the left' is a reversal indicator (reading from right to left).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'gathered' indicates anagramming the letters.
'red' written backwards gives 'der'.
'acorn'+'i'='acorni'
'acorni' with letters rearranged gives 'corian'.
'der' put after 'corian' is 'CORIANDER'.
(Other definitions for coriander that I've seen before include "Parsley-like herb used in cooking" , "Spice" , "Herb used with carrot for soup" , "Culinary herb" , "ingredient of coronation chicken?" .)