Doctors covering area must get breaks (4)
I believe the answer is:
gaps
'breaks' is the definition.
('gap' can be a synonym of 'break')
'doctors covering area' is the wordplay.
'doctors' becomes 'gps' (GP is an example).
'covering' indicates putting letters inside.
'area' becomes 'a' (maths abbreviation).
'gps' placed around 'a' is 'GAPS'.
'must get' is the link.
(Other definitions for gaps that I've seen before include "Breaks, spaces" , "Breaks or openings as in hedge or fence" .)