Rough? That's odd! (6)
I believe the answer is:
uneven
'odd' is the definition.
(odd rather than even)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for uneven that I've seen before include "Not level or smooth" , "Rough, jagged" , "Ill-matched - irregular" , "Not uniform or smooth" , "That's odd" .)