Word used in clint eastwood films. It is used to exaggerate the word fuck rather than calling him a fuck or fuck head it is made funny by making it a cluster of fuck.
Hey Fat Boy get up off the ground and do something you cluster of fuck (normally said by gym teachers)
A cluster offender is a person who has an incredible ability to offend a large mass of people at the same time usually without any knowledge of what they're doing.
This can often be observed at important gatherings such as parties, weddings and funerals.
(At a wedding)
You: Unless a woman carries my bag for me then she won't be compliant and therefore wont suck my cock
Sally: You're an ass Pauline: Oh my god you're a cluster offender, we're leaving