Jack in Blockbuster for Dynasty, that’s becoming addictive (5-7)
I believe the answer is:
habit-forming
'addictive' is the definition.
(I've seen this before)
'jack in blockbuster for dynasty' is the wordplay.
'jack in blockbuster' becomes 'habit' (I can't justify this - if you can you should believe this answer much more).
'dynasty' becomes 'ming' (Ming dynasty of China).
'habit'+'for'+'ming'='HABIT-FORMING'
'that's becoming' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for habit-forming that I've seen is " Addictive".)