Force bishop to leave shelter to plough (6)
I believe the answer is:
furrow
'plough' is the definition.
(both can mean a trench)
'force bishop to leave shelter' is the wordplay.
'force' becomes 'f' (symbol used in Physics e.g. f=ma).
'bishop' becomes 'b' (abbreviation used in chess).
'to leave' is a deletion indicator.
'shelter' becomes 'burrow'.
'burrow' with 'b' removed is 'urrow'.
'f'+'urrow'='FURROW'
'to' acts as a link.
(Other definitions for furrow that I've seen before include "Ploughing mark" , "Shallow trench made by a plough" , "Long cut in ground made by plough" , "Plough's rut" , "It's groovy!" .)