Ordered Tolkien monster to swallow one horse up (7)

I believe the answer is:
organic
'ordered' is the definition.
Both the answer and definition are adjectives. Maybe you can see an association between them that I don't see?
'tolkien monster to swallow one horse up' is the wordplay.
'tolkien monster' becomes 'orc' (orcs are creatures in The Lord of the Rings).
'to swallow' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'horse' becomes 'nag' (term for an old horse).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'i'+'nag'='inag'
'inag' in reverse letter order is 'gani'.
'orc' enclosing 'gani' is 'ORGANIC'.
Can you help me to learn more?
(Other definitions for organic that I've seen before include "without the use of chemicals" , "sort of farming" , "Chemical and GM free" , "Got from living matter" , "Derived from living matter" .)
