It's just a cryptic crossword clue. People hate these. One half of the clue is like a definition of the answer, and the other half is like a punny, supposedly clever play upon the answer. But it's not obvious which side is which, or where the division is. (8) is the number of letters in the answer. The wordplay part is "except a unit of hair." "A unit of hair" here is TRESS, and "except" is BUT. So the answer is BUTTRESS, which is a type of support. Good job.