Ignorant uncle starts a war with the second generation (7)
I believe the answer is:
unaware
'ignorant' is the definition.
(I've seen this before)
'uncle starts a war with the second generation' is the wordplay.
'uncle starts' becomes 'una' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'with' means one lot of letters go next to another.
'the second generation' becomes 'e' (nnd letter of 'generation').
'una'+'war'+'e'='UNAWARE'
Can you help me to learn more?
(Other definitions for unaware that I've seen before include "Uninformed" , "Not cognisant" , "Unexpected" , "Not having knowledge or realisation" , "Not informed - ignorant (of)" .)