Start of crossword clue, ending with unknown material (6)
I believe the answer is:
chintz
'material' is the definition.
(chintz is a kind of material)
'start of crossword clue ending with unknown' is the wordplay.
'start of' suggests taking the first letters.
'clue' becomes 'hint' ('hint' can be a synonym of 'clue').
'ending' means one lot of letters go next to another.
'with unknown' becomes 'z' (algebra. I am not sure about the 'with' bit.**).
The first letter of 'crossword' is 'c'.
'c'+'hint'+'z'='CHINTZ'
Can you help me to learn more?
(Other definitions for chintz that I've seen before include "Printed multi-coloured cotton fabric" , "Glazed cotton print" , "Printed cotton fabric for curtains or upholstery" , "Patterned fabric for soft furnishings" , "Floral cotton cloth" .)