How to add an audio effect to only one bit of a clip?

[graceslick]

I love certain of the audio effects and want to add them to clips, but how do I confine them to only part of a clip and not the whole clip?

My process is, I am recording my clip and then adding whatever audio effect I want...but again, how do I add it to only a part (say, the very beginning, and then I want to remove it and replace it with another one, for instance)?

Thank you

[longjohns]

there are envelopes on a clip for whatever FX are on that track

(session view)

so you would create envelopes for each effect, at the relevant parts of the clip. including 'device on/off' or 'dry/wet'