Doctor taking a break (3)
I believe the answer is:
gap
'break' is the definition.
(a gap is a break in something)
'doctor taking a' is the wordplay.
'doctor' becomes 'gp' (general practitioner).
'taking' is an insertion indicator.
'gp' placed around 'a' is 'GAP'.
(Other definitions for gap that I've seen before include "Interval, break" , "Breach or lacuna" , "A small parting, in hedge or teeth" , "Fissure" , "Aperture" .)