Surrounded by charity collecting millions (4)
I believe the answer is:
amid
'surrounded by' is the definition.
(amid means among or surrounded by)
'charity collecting millions' is the wordplay.
'charity' becomes 'aid' (eg foreign aid).
'collecting' means one lot of letters goes inside another.
'millions' becomes 'm' (abbreviation).
'aid' going around 'm' is 'AMID'.
(Other definitions for amid that I've seen before include "Within" , "A dim sort of preposition" , "Surrounded by" , "In the course of" , "Maid (anag)" .)