The Sun
Water in clouds or anywhere else is a compound, as long as it doesn't have dissolved solids in it (as in fresh water). If it has solids or anything else dissolved in it, then it is a mixture (solution).
Photosynthesis needs sunlight & carbon dioxide besides water
Besides these Energy is produced.
bones and meat
Many gases, such as helium.
trees, bushes, mud,
Minerals from the soil.
heat or hot water
Acids reacts with bases to form a salt and water.
Clouds have to do with water because water vapor precipitates into the clouds.
Clouds do not 'carry' water, clouds are composed of water vapor.