Occasionally there is a clan symbol listed along with all the troops an attacker used in my defense log after I;ve been attacked. Does this mean the attacker is using borrowed troops from his clan mates for the attack? Since I don't belong to a clan and do individual combat only, this doesn't seem fair. Also is there any way to send a private message to someone in the game or are you restricted to the global chat? Thanks for any help!
Yes, you are correct. The clan flag symbol listed with the troops that they used means that they deployed troops given to they by another player in their clan. Check this link out for more info on the clan castle and it's functions: http://clashofclans.wikia.com/wiki/Clan_Castle.
There is no way to communicate with other players except through the global channel, your clan chat, and clan mail (so no private messaging).
While it might seem unfair that someone can use troops given to them by their clan, a large portion of the game is based around players being a part of a clan (it's even in the name - Clash of 'Clans'). Joining a clan can provide many benefits, and sooner or later, you should - and probably will - join one.
In a clan, you can request troops to be donated by your clan mates. This is limited to 10-25 housing space depending on Clan Castle level. Additionally, troops in a Clan Castle will defend against an attack. However it's useful to know that Clan Castle troops are used the same way as regular troops; once they're used to attack or defend, they're gone. This is a good incentive to find yourself a clan.
Chat is limited to global chat and clan chat, there is no private chat ability.