Mount Snowdon – oddly abandoned and private (3)
I believe the answer is:
own
'private' is the definition.
(as in one's own or private belongings)
'mount snowdon oddly abandoned' is the wordplay.
'mount' shows that the letters should be reversed in order (I've seen 'mounting' mean this (going up in a down clue)).
'oddly abandoned' indicates alternate letters (letters in odd-numbered positions removed).
The alternate letters of 'snowdon' are 'nwo'.
'nwo' written backwards gives 'OWN'.
'and' is the link.
(Other definitions for own that I've seen before include "Control" , "Personal; possess" , "Possess or confess" , "Allow" , "Possess - recognise - admit" .)