Climber pocketing gold key (5)
I believe the answer is:
ivory
'key' is the definition.
(I've seen this before)
'climber pocketing gold' is the wordplay.
'climber' becomes 'ivy' (I've seen this before).
'pocketing' is an insertion indicator.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'ivy' going around 'or' is 'IVORY'.
(Other definitions for ivory that I've seen before include "pasty" , "Hard creamy-white dentine used for making ornaments" , "Film director" , "Creamy-white colour" , "Some hunt this" .)