Never seen a spring clamp on a Citroen/Peuget so I guess you mean one of these horrible things
(That picture shows them before they are crimped) I usually attack the crimped part with a screwdriver and long nosed plyers to revert the crimp to that picture above, and then flatten it completely to a circle, then slide the clamp away from the join, remove hose etc.
Good luck getting it started. If it was me I'd be inclined just to tow it (down a nearby deserted road / car park) in second gear (assuming it's manual) for however long it takes.
A tale of woe
Moderator: RichardW