12 across
One
in
five
heading
to
Open
are
seeds
(6)
One in five heading to Open are seeds (6)
hints
0
checks
0
hints
The definition is at the end of the clue.
How the clue works
QUIN is one in five (a quintuplet), then the headings (first letters) of "Open are" give O and A, all leading to seeds (quinoa being a seed crop).