Give a big donation (5)
I believe the answer is:
endow
'give a big donation' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for endow that I've seen before include "Give funding to establish (something)" , "Enrich with a gift or faculty" , "Enrich (with a facility or gift)" , "Establish (university post) by giving funds" , "Set up with money" .)