The Report has a Preview Queue with the WMF page file names. You could try deleting all but the 1st record from that Queue.
If that does not work you could also try to REMOVE() the WMF files when you delete from the Queue.
AFAIK even though you remove the WMF from the QUEUE the RTL keeps its own shadow list and still deletes them all the from Temp folder.
The other way I recall doing this is to define another Report then building its Preview Queue as Copies of WMF files from the Original Report. I know that is how you merge 2 reports.
For anyone using a lot of Clarion Reports I suggest regularly running a Temp folder clean up on end user machines as there can be orphan WMF’s due to crashes or the user shutting down the program. On old systems when I implement this I typically find 1000’s of files.