Climber pocketing gold -- it's an ornamental material (5)
I believe the answer is:
ivory
'an ornamental material' is the definition.
'ivory' can be an answer for 'material' (ivory is a kind of material). I'm not sure about the 'an ornamental' bit.
'climber pocketing gold' is the wordplay.
'climber' becomes 'ivy' (ivy is a climbing plant).
'pocketing' is an insertion indicator (pocket can mean to steal or take possession of).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'ivy' going around 'or' is 'IVORY'.
'it's' is the link.
Can you help me to learn more?
(Other definitions for ivory that I've seen before include "Like the tower" , "National emblem" , "Off-white colour" , "Country on the Gulf of Guinea, a former French protectorate" , "Material from tusks of certain mammals" .)