Good weather for cereal crops (5)
I believe the answer is:
grain
'cereal crops' is the definition.
(I've seen this before)
'good weather' is the wordplay.
'good' becomes 'g' (abbreviation).
'weather' becomes 'rain' (rain is a kind of weather).
'g'+'rain'='GRAIN'
'for' is the link.
(Other definitions for grain that I've seen before include "little salty bit" , "Smallest measure of weight in avoirdupois" , "Direction of fibres found in wood" , "Small hard particle, of rice perhaps" , "Small particle - weight" .)