Riffer on iOS standalone and midi clock with external gear

Hello all, I’m looking for a way to sync Riffer standalone on iOS with an external sequencer that sends MIDI Clock. I can’t find anything in the MIDI preferences.
This is very useful if I want to create random sequences on the fly on the external sequencer.
I can send and receive notes to/from the sequencer but not sync it so that, when I press Play on it, Riffer also starts.
When it works inside AUM or Drambo it works perfectly but I don’t want to use other apps.
Thanks