Hi Dylan,
11 - single letter for "cousin's first" + 2 letters for "dealing with" + 7 letters for "chemistry for example" - it's a common or well known word but I had no idea it means "my" Scottish - but it does!
28 - was my last one in - it's the name of a singer (who, needless to say, I'd never heard of) and is a sort of cryptically humorous phrase (5,2) that could mean " sartorial need for church choir?"
30 - single letter for "one" + 4 letter "border" minus last letter/"almost" all inside a 5 letter "moat" - definition is "preserve former life".