Small ice art (5)
I believe the answer is:
skill
'art' is the definition.
(I've seen this before)
'small ice' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'ice' becomes 'kill' (ice can informally mean to kill or assassinate).
's'+'kill'='SKILL'
(Other definitions for skill that I've seen before include "Special ability" , "Ability - dexterity" , "Craft; dexterity" , "Knack" , "Prowess" .)