Ancient marker gripped by climber (7)
I believe the answer is:
vintage
'ancient' is the definition.
(both can mean old)
'marker gripped by climber' is the wordplay.
'marker' becomes 'tag' (tag is a kind of marker).
'gripped by' indicates putting letters inside.
'climber' becomes 'vine' (climbing plant).
'tag' inserted within 'vine' is 'VINTAGE'.
(Other definitions for vintage that I've seen before include "Period of origin" , "High-quality wine" , "Good quality (wine)" , "Type of wine" , "Wine harvest" .)