Oblique-angled parallelogram (7)
I believe the answer is:
rhombus
'oblique-angled parallelogram' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for rhombus that I've seen before include "Four-sided figure" , "Diamond shape" , "Special case of parallelogram" , "Large bottle; vessel with spout" , "Type of parallelogram" .)