Donate four keys outside (4)
I believe the answer is:
give
'donate' is the definition.
(I know that donate is a more specific form of the action give)
'four keys outside' is the wordplay.
'four' becomes 'IV' (Roman numerals).
'keys' becomes 'ge' (I am not sure about this - if you are sure you should believe this answer much more).
'outside' indicates putting letters inside.
'iv' inserted within 'ge' is 'GIVE'.
Can you help me to learn more?
(Other definitions for give that I've seen before include "old-fashioned shackle" , "Contribute - elasticity" , "Hold out" , "concede" , "Offer, elasticity" .)