Cut round grainy design? (4,6)
I believe the answer is:
crop circle
'grainy design?' is the definition.
(design in a field of grain)
'cut round' is the wordplay.
'cut' becomes 'crop' (cropping is a kind of cutting).
'round' becomes 'circle' (synonyms).
'crop'+'circle'='CROP CIRCLE'
(Other definitions for crop circle that I've seen before include "Hertfordshire new town" , "mysterious country area" .)