One may exert pressure (4)
I believe the answer is:
peer
'one may exert pressure' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for peer that I've seen before include "Member of the House of Lords" , "Look hard through narrowed eyes" , "count, perhaps" , "Look hard at the nobleman" , "Look searchingly at lord?" .)