Are you a PAL or NTSC user?
In short, export from Streamclip to a matching Quicktime file.
First, go to FCE>Easy Setup and look at the properties of each one (read the fine print).
Select the Easy Setup that matches your orignal footage the closest, frame size, video standard, frame rate and audio.
Then setup Streamclip to produce an export to Quicktime that exactly matches the chosen FCE Easy Setup.
If they both match there will be no rendering.
Note: If the Easy Setup is changed, only NEW Sequences are changed not existing ones.
This means you also need to make sure the FCE Seqeunce that the export is edited into matches the settings.
Check this by right clicking on the Sequence icon in the Browser and select Item Properties.