Thin as a rake (4)
I believe the answer is:
lean
This clue is a double definition.
'thin' is the first definition.
('lean' is associated in meaning with 'thin')
'a rake' is the second definition.
(thesaurus)
'as' acts as a link.
(Other definitions for lean that I've seen before include "Insufficient - incline" , "Unprofitable" , "without success" , "Thin; heel" , "Without excess flesh" .)