Doctors travel in time (8)
I believe the answer is:
interval
'time' is the definition.
(thesaurus)
'doctors travel in' is the wordplay.
'doctors' indicates anagramming the letters.
'travel'+'in'='travelin'
'travelin' anagrammed gives 'INTERVAL'.
(Other definitions for interval that I've seen before include "Time break as in play production" , "Pause (between acts)" , "in which cast rests?" , "A break as in travel" , "Break in activity" .)