Decompression sickness (3,5)
I believe the answer is:
the bends
'decompression sickness' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for the bends that I've seen before include "on high mountain roads?" , "suffering when going under?" , "Sickness which drivers must watch out for" , "Decompression sickness; Radiohead album" , "A risk for divers" .)