Almost a disaster — point to what should prevent a shock (4,5)
I believe the answer is:
near thing
'almost a disaster' is the definition.
(I've seen this before)
'point to what should prevent a shock' is the wordplay.
'point' becomes 'n' (N is an example).
'to what should prevent a shock' becomes 'earthing' (earthing should prevent electric shocks).
'n'+'earthing'='NEAR THING'
(Other definitions for near thing that I've seen before include "Something that barely avoids failure or disaster" , "Narrow escape, missed by a small margin (4.5)" , "Knife-edge event" , "Even the short-sighted could plainly see that" , "almost an accident" .)