With effect of sun, it grows (5)
I believe the answer is:
wheat
'it grows' is the definition.
The definition suggests a singular noun which matches the answer.
'with effect of sun' is the wordplay.
'with' becomes 'w' (abbreviation).
'effect of sun' becomes 'heat' (I can't justify this - if you can you should give a lot more credence to this answer).
'w'+'heat'='WHEAT'
Can you help me to learn more?
(Other definitions for wheat that I've seen before include "Grain crop" , "Grass whose grain is used to make flour" , "Cereal for bread/pasta" , "Cereal grass" , "Type of cereal" .)