Part — of backward Time Lord? (4)
I believe the answer is:
role
'part' is the definition.
(synonyms)
'of backward time lord?' is the wordplay.
'backward' says the letters should be written backwards.
'of' indicates a hidden word.
'elor' is hidden within 'time lord'.
'elor' in reverse letter order is 'ROLE'.
(Other definitions for role that I've seen before include "Part in play, film etc" , "Impersonation" , "Playing part" , "A part of lore" , "Duty" .)