Symptom of tetanus (7)
I believe the answer is:
lockjaw
'symptom of tetanus' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for lockjaw that I've seen before include "Graphic word for tetanus" , "trap closer" , "Form of tetanus in which mouth is tightly closed" , "Symptom of tetanus" , "Form of tetanus with rigidly closed mouth" .)