Factory scheme finally right (5)
I believe the answer is:
plant
'factory' is the definition.
(I've seen this in another clue)
'scheme finally right' is the wordplay.
'scheme' becomes 'plan' (synonyms).
'finally' says to take the final letters.
The last letter of 'right' is 't'.
'plan'+'t'='PLANT'
(Other definitions for plant that I've seen before include "Set; factory" , "Hide incriminating evidence" , "Member of vegetable kingdom" , "eg Flower" , "Spy; manufacturer's site" .)