A new don in a bed deserted (9)
I believe the answer is:
abandoned
'deserted' is the definition.
('abandon' can be a synonym of 'desert')
'a new don in a bed' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'in' indicates putting letters inside.
'a'+'n'+'don'='andon'
'a'+'bed'='abed'
'andon' placed within 'abed' is 'ABANDONED'.
(Other definitions for abandoned that I've seen before include "Profligate - gave up - left" , "Given up?" , "Forsook, left behind" , "Left in the lurch, forsaken" , "Unrestrained" .)