Bishop runs to a ship (4)
I believe the answer is:
boat
'ship' is the definition.
(thesaurus)
'bishop runs to a' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'runs' is an anagram indicator.
'to'+'a'='toa'
'toa' with letters rearranged gives 'oat'.
'b'+'oat'='BOAT'
(Other definitions for boat that I've seen before include "See 1" , "Small vessel" , "Vessel for travelling on water" , "Contest on the Thames" , "See 18" .)