Sign over pieces (4)
I believe the answer is:
omen
'sign' is the definition.
(omen is a kind of sign)
'over pieces' is the wordplay.
'over' becomes 'o' (cricket abbreviation).
'pieces' becomes 'men' (e.g. in chess).
'o'+'men'='OMEN'
(Other definitions for omen that I've seen before include "Augur" , "Harbinger, augury" , "Forecast" , "Augury, portent" , "Harbinger, portent" .)