Free from material constraints, doctor sided with boy hiding spy (9)
I believe the answer is:
disembody
'free from material constraints' is the definition.
'doctor sided with boy hiding spy' is the wordplay.
'doctor' indicates an anagram.
'with' is a charade indicator (letters next to each other).
'hiding' is an insertion indicator.
'spy' becomes 'M' (in the James Bond movies/books).
'sided' put after 'boy' is 'boysided'.
'boysided' is an anagram of 'disebody'.
'disebody' going around 'm' is 'DISEMBODY'.
(Other definitions for disembody that I've seen before include "Release spirits" , "Some biddy (anag)" .)