Second murder in facility (5)
I believe the answer is:
skill
'facility' is the definition.
(I've seen this in another clue)
'second murder' is the wordplay.
'second' becomes 's' (common abbreviation).
'murder' becomes 'kill' (I've seen this before).
's'+'kill'='SKILL'
'in' acts as a link.
(Other definitions for skill that I've seen before include "Special ability" , "Ability acquired by training" , "Expertise, dexterity" , "Talent" , "Knack" .)