This is the 12475th most frequent Russian word.
клевера
"Клевера" means "clovers" (plural form).
Here, 'клевера' is used in the genitive singular form to denote belonging or description of the noun 'цветков' as a type of clover.
В поле было много красных цветков клевера.
In the field, there were many red flowers of clover.
Here, 'клевера' is also in the genitive singular form, indicating possession or characteristic of 'листьями' being the leaves of the plant clover.
Ветер играл с листьями клевера.
The wind played with the leaves of clover.
In this example, 'клевера' is used in the genitive singular form as part of the expression 'из нежного клевера,' specifying 'клевера' as the material or origin of the bouquet.