Jab, nudge (4)
I believe the answer is:
prod
This clue is a double definition.
'jab' is the first definition.
(I know that jab can be written as prod)
'nudge' is the second definition.
(I know that nudge can be written as prod)
(Other definitions for prod that I've seen before include "Poke with a stick" , "Incite to action (with a stick?)" , "Poke; reminder" , "Poke, jab, nudge" , "Stimulus" .)