Shift interrupted by constant disagreement (11)
I believe the answer is:
altercation
'disagreement' is the definition.
(altercation is a kind of disagreement)
'shift interrupted by constant' is the wordplay.
'shift' becomes 'alter' (I've seen this before).
'interrupted by constant' becomes 'cation' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'alter'+'cation'='ALTERCATION'
Can you help me to learn more?
(Other definitions for altercation that I've seen before include "One's argued" , "Spat" , "heated dispute" , "Rattle a coin (anag) - row" , "Noisy disagreement" .)