Doughnut, say, consumed by doctor usually (5)
I believe the answer is:
torus
'doughnut' is the definition.
(I've seen this before)
'consumed by doctor usually' is the wordplay.
'consumed by' says the answer is hidden in the clue (inserted letters get consumed).
'TORUS' is hidden within 'doctor usually'.
'say' is the link.
(Other definitions for torus that I've seen before include "Ring shape" , "Architectural moulding" , "Shape of doughnut" , "Doughnut-shaped figure" , "Ring shaped like doughnut with hole" .)