Very productive
'very productive' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for prolific that I've seen before include "Producing fruit in abundance" , "Producing a great amount, as writer may" , "Copious" , "Abundant in growth" , "Highly productive, fruitful" .)
'very productive' is the definition.
(I know this)
This is all the clue.
(Other definitions for fertile that I've seen before include "(Of soil) rich" , "Fecund" , "Abundantly productive" , "Capable of growing or reproducing" , "Rich in resources" .)