Ornamental stone jardiniere initially manufactured, first off (4)
I believe the answer is:
jade
'ornamental stone' is the definition.
'jardiniere initially manufactured first off' is the wordplay.
'initially' suggests taking the first letters.
'manufactured' becomes 'made' (I've seen this before).
'first off' means to remove the first letter.
The first letter of 'jardiniere' is 'j'.
'made' with its initial letter taken away is 'ade'.
'j'+'ade'='JADE'
(Other definitions for jade that I've seen before include "Green gemstone" , "Ornamental semiprecious stone" , "Worthless horse" , "Worn-out horse" , "Mount" .)