Aggression from Uncle Dicky breaking peace (10)
I believe the answer is:
truculence
'aggression' is the definition.
(I've seen this before)
'uncle dicky breaking peace' is the wordplay.
'dicky' indicates anagramming the letters (dicky can mean ill or non-functioning).
'breaking' means one lot of letters goes inside another.
'peace' becomes 'truce' (truce is a kind of peace).
'uncle' is an anagram of 'ulenc'.
'ulenc' put within 'truce' is 'TRUCULENCE'.
'from' acts as a link.
(Other definitions for truculence that I've seen before include "Aggressive defiance" , "Aggression" , "Bellicosity" .)