Apply pressure (4)
I believe the answer is:
urge
'apply pressure' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for urge that I've seen before include "Try hard to persuade, advise earnestly" , "Encourage (to do something)" , "Constrain" , "Incite to action" , "Encourage or entreat earnestly" .)