Contribution from Russian leader put to the bottom (5)
I believe the answer is:
input
'contribution from russian leader' is the definition.
'input' can be an answer for 'contribution' (I've seen this before). I am not certain of the 'from russian leader' bit.
'put to the bottom' is the wordplay.
'to' says to put letters next to each other (I've seen this in other clues).
'the bottom' becomes 'in' (I can't explain this - if you can you should believe this answer much more).
'put' put after 'in' is 'INPUT'.
Can you help me to learn more?
(Other definitions for input that I've seen before include "Data etc supplied to computer" , "supply" , "Data entry" , "Resource" , "Simple, without artifice" .)