Plant maize occasionally at the side of a pasture (6)
I believe the answer is:
azalea
'plant' is the definition.
(type of plant)
'maize occasionally at the side of a pasture' is the wordplay.
'occasionally' indicates alternate letters.
'at the side of' means one lot of letters go next to another.
'pasture' becomes 'lea' (both can mean a field).
The alternate letters of 'maize' are 'az'.
'az'+'a'+'lea'='AZALEA'
(Other definitions for azalea that I've seen before include "Shrub with brightly coloured flowers" , "Rhododendron-like plant" , "Rhododendron relative" , "Flowering shrub akin to rhododendron" , "flower" .)