Force politician into middle of field (5)
I believe the answer is:
impel
'force' is the definition.
(I know that force can be written as impel)
'politician into middle of field' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'into' indicates putting letters inside.
'middle of' means to look at the middle letters.
The middle of 'field' is 'iel'.
'mp' going inside 'iel' is 'IMPEL'.
(Other definitions for impel that I've seen before include "Urge forward, drive" , "Spur on" , "Constrain" , "Urge or drive to do something" , "Motivate" .)