Make a contribution to the same neat arrangement (6)
I believe the answer is:
donate
'make a contribution' is the definition.
(I've seen this in another clue)
'the same neat arrangement' is the wordplay.
'the same' becomes 'do' (abbreviation for ditto).
'arrangement' is an anagram indicator.
'neat' with letters rearranged gives 'nate'.
'do'+'nate'='DONATE'
'to' is the link.
(Other definitions for donate that I've seen before include "Muhammad -, US boxer" , "Make a gift of" , "Give - present" , "Contribute (to charity)" , "Give freely, maybe blood" .)