Power, possibly will (5)
I believe the answer is:
might
I believe this is a double definition.
'power' is the first definition.
(I know that power can be written as might)
'possibly will' is the second definition.
(if you might do something, you will possibly do it)
(Other definitions for might that I've seen before include "is not unlikely to" , "intensity of feeling" , "Force; could" , "Capability" , "Clout" .)