When you say 'offer' - was this definitely confirmed via UCAS or just 'over the phone'?
'We'll look at your application, so please apply through Clearing' isnt an offer.
And any University can look at a Clearing application, decide they dont want you, and reject your Clearing application.
However, if you actually had a confirmed offer (UF) through UCAS then you have every right to be annoyed.
Contact the Head of Admissions at that Uni with full details.