Unrewarding tip (4)
I believe the answer is:
lean
I believe this is a double definition.
'unrewarding' is the first definition.
(lean can mean offering very little)
'tip' is the second definition.
(synonyms)
(Other definitions for lean that I've seen before include "Inclination" , "Meagre" , "The fatless part of the meat" , "Of meat, with little or no fat" , "Thin; rest (against)" .)