Go green, perhaps, by the end of July (6)
I believe the answer is:
energy
'go' is the definition.
(thesaurus)
'green perhaps by the end of july' is the wordplay.
'perhaps' is an anagram indicator.
'by' is a charade indicator (letters next to each other).
'the end of' says to take the final letters.
The final letter of 'july' is 'y'.
'green' with letters rearranged gives 'energ'.
'energ'+'y'='ENERGY'
(Other definitions for energy that I've seen before include "Vigour, power" , "Zeal" , "Vitality, power" , "Go green, possibly with envy, ultimately" , "It's measured in joules or ergs" .)