Failed first oral about plants (5)
I believe the answer is:
flora
'plants' is the definition.
(I've seen this before)
'failed first oral about' is the wordplay.
'failed first' becomes 'f' (1st letter of 'failed').
'about' indicates an anagram.
'oral' with letters rearranged gives 'lora'.
'f'+'lora'='FLORA'
(Other definitions for flora that I've seen before include "For example, Miss Macdonald" , "Plant life of particular area" , "Roman goddess of flowers" , "Plants < girl" , "The plants of an area (5)" .)