Get good and thin (5)
I believe the answer is:
glean
'get' is the definition.
(thesaurus)
'good and thin' is the wordplay.
'good' becomes 'g' (abbreviation).
'and' means one lot of letters go next to another.
'thin' becomes 'lean' ('lean' is associated in meaning with 'thin').
'g'+'lean'='GLEAN'
(Other definitions for glean that I've seen before include "Gather (info or the harvest)" , "Collect grain (or information?)" , "Pick up (information)" , "Gather remnants of corn" , "Pull together from various sources" .)