Farm animals always knocked over orchid (8)
I believe the answer is:
cattleya
'orchid' is the definition.
(I know that Cattleya is a type of orchid)
'farm animals always knocked over' is the wordplay.
'farm animals' becomes 'cattle' (I've seen this before).
'always' becomes 'ay' (archaic term for 'always').
'knocked over' shows that the letters should be reversed in order.
'ay' backwards is 'ya'.
'cattle'+'ya'='CATTLEYA'
(Other definitions for cattleya that I've seen before include "bright orchid" , "US orchid that's showy" , "exotic plant" .)