Difference of opinion when lineage is mentioned? (7)
I believe the answer is:
dissent
'difference of opinion' is the definition.
(I've seen this before)
'lineage is mentioned?' is the wordplay.
'lineage' becomes 'descent' ('descent' can be a synonym of 'lineage').
'is mentioned?' shows a homophone (sound like).
'descent' sounds like 'DISSENT'.
'when' acts as a link.
(Other definitions for dissent that I've seen before include "Differ" , "Open disagreement" , "Not agree" , "Opposition" , "Express a different opinion" .)