Physician used seer's vanity (7)
I believe the answer is:
dresser
'vanity' is the definition.
(I know that vanity can be written as dresser)
'physician used seer's' is the wordplay.
'physician' becomes 'Dr' (synonyms).
'used' is an anagram indicator.
'seers' is an anagram of 'esser'.
'dr'+'esser'='DRESSER'
(Other definitions for dresser that I've seen before include "Tool for smoothing" , "employed off stage" , "one coming into line?" , "Person working in one theatre" , "clotheshorse?" .)