Siren alerts cover this potentially fatal type of failure (5)
I believe the answer is:
renal
'potentially fatal type of failure' is the definition.
I can't judge whether this defines the answer.
'siren alerts cover' is the wordplay.
'cover' indicates a hidden word (I've seen 'covered' mean this (the answer is covered up by the clue)).
'RENAL' is hidden within 'siren alerts'.
'this' is the link.
Can you help me to learn more?
(Other definitions for renal that I've seen before include "like kidneys" , "Concerned with organ" , "around the kidney" , "using the reins" , "Pertaining to the kidneys" .)