Disagree over some nuclear issue (4,3)
I believe the answer is:
fall out
This could be a double definition.
'disagree' is the first definition.
(I've seen this before)
'some nuclear issue' is the second definition.
'fall out' can be an answer for 'issue' (thesaurus). I am not certain of the 'some nuclear' bit.
'over' acts as a link.
Can you help me to learn more?
(Other definitions for fall out that I've seen before include "Radioactive pollution" , "disagree" , "Quarrel - leave the ranks" , "Happen" .)