Chief over in black ship (4)
I believe the answer is:
boss
'chief' is the definition.
(synonyms)
'over in black ship' is the wordplay.
'over' becomes 'o' (cricket abbreviation).
'in' means one lot of letters goes inside another.
'black' becomes 'b' (as in pencil classifications).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'b'+'ss'='bss'
'o' put inside 'bss' is 'BOSS'.
(Other definitions for boss that I've seen before include "Informal employer or superior" , "Domineer" , "Head honcho" , "Gaffer, manager" , "(One's) chief" .)