Advice to buyer: try timeless ring owned by speleologist (6,6)
I believe the answer is:
caveat emptor
'advice to buyer' is the definition.
('let the buyer beware' in Latin)
'try timeless ring owned by speleologist' is the wordplay.
I cannot really see how this works, but
'ring' could be 'o' (O is the shape of a ring) and 'o' is located in the answer.
'by' could be 'at' and 'at' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for caveat emptor that I've seen before include "at your own risk" , "Warning to buyers" , "Commercial advice" , "Let the buyer beware (Latin)" , "purchasing principle" .)