Produce good line (4)
I believe the answer is:
grow
'produce' is the definition.
(I know that produce can be written as grow)
'good line' is the wordplay.
'good' becomes 'g' (abbreviation).
'line' becomes 'row' (a row or line of things).
'g'+'row'='GROW'
(Other definitions for grow that I've seen before include "Burgeon" , "Expand" , "Become larger" , "Gain in size" , "Become bigger" .)