Abuse of pills by accident (5)
I believe the answer is:
spill
'accident' is the definition.
(I've seen this before)
'abuse of pills' is the wordplay.
'abuse of' is an anagram indicator (I've seen 'abuse' mean this).
'pills' anagrammed gives 'SPILL'.
'by' acts as a link.
(Other definitions for spill that I've seen before include "Cause liquid to overflow" , "Upset - lighter" , "Overturn" , "Cause liquid to flow from a container" , "Fire lighter; reveal (confidential information)" .)