Less productive apprentice runs away (6)
I believe the answer is:
leaner
'less productive' is the definition.
(I've seen this before)
'apprentice runs away' is the wordplay.
'apprentice' becomes 'learner' ('learner' can be a synonym of 'apprentice').
'runs' becomes 'r' (cricket abbreviation).
'away' is a deletion indicator.
'learner' with 'r' taken away is 'LEANER'.
(Other definitions for leaner that I've seen before include "less productive" , "One with an inclination" , "Thinner, with less fat" , "less corpulent?" , "less bulky" .)