Look - sloth runs (3)
I believe the answer is:
air
'look' is the definition.
(I've seen this before)
'sloth runs' is the wordplay.
'sloth' becomes 'ai' (ai is a kind of sloth).
'runs' becomes 'r' (cricket abbreviation).
'ai'+'r'='AIR'
(Other definitions for air that I've seen before include "Expose" , "Look - warm and dry" , "character" , "Publish" , "Atmosphere surrounding the earth" .)