Get worse again (7)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
relapse
'get worse again' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for relapse that I've seen before include "Deteriorate after getting better" , "Return to sickness" , "Become ill again" , "Regress, fall back" , "causing setback to recovery" .)