Reviewing as I hear
The vocals in the beginning were nice. I like the tail on the snare, and the added in bass with hard noises. It gives the song the sort of hardstyle emotion, and sound. The good thing is that you keep adding sounds to keep the flow going.
One thing i do dislike is the way you faded out those sounds maybe try an EQ fade on all the sounds? I like how you synced and reverbed those vocals, with your piano.
Your melody fade in with those vocals is very original, I don't see it happen much, though its a good transition.
I like your melody, everything is perfect (unlike my pieces lol :P)
I think a better outro would have been another piano melody without a fade in, more like a sudden-ish sort of stop.
Overall, this has minor things, which arent a big deal.
Answer to your question. Use a balance or volume automation along with the low pass filter at the the perfect amount to not have clicking. You can also try another frequency on the EQ filters to go along with that one, thus eliminating clicking.