Stimulate or pressure staff (4)
I believe the answer is:
prod
'stimulate' is the definition.
(thesaurus)
'pressure staff' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'staff' becomes 'rod' (I've seen this before).
'p'+'rod'='PROD'
'or' is the link.
(Other definitions for prod that I've seen before include "Give a reminder" , "Goad, stimulate into action" , "Poke or spur" , "Poke - remind" , "Push with pointed instrument" .)