Noughts on end of digit in addition (3)
I believe the answer is:
too
'in addition' is the definition.
(I've seen this before)
'noughts on end of digit' is the wordplay.
'noughts' becomes 'oo' (I can't explain this - if you can you should give a lot more credence to this answer).
'on' means one lot of letters go next to another.
'end of' says to take the final letters.
The last letter of 'digit' is 't'.
'oo' after 't' is 'TOO'.
Can you help me to learn more?
(Other definitions for too that I've seen before include "Moreover, in addition" , "Furthermore" , "Excessively" , "To a greater than desirable extent" , "Additionally" .)