Interest (7)
'interest' is the definition.
(I know that interest is a kind of concern)
This is the entire clue.
(Other definitions for concern that I've seen before include "Business - anxiety" , "Involve" , "Disquiet" , "Relate to; anxiety" , "Cause of anxiety" .)
'interest' is the definition.
(I know that behalf is a type of interest)
This is all the clue.
(Other definitions for behalf that I've seen before include "(On someone's) account" , "(On one's) account" , "Sake, interest, benefit" , "(Someone's) benefit or sake" , "(A person's) interest" .)
'interest' is the definition.
(vested interest is a kind of interest)
This is the entire clue.
(Other definitions for vested that I've seen before include "This interest has expectations of gain" , "Interests may be" , "Interest that is personal, often for financial gain" , "This sort of interest means having a personal involvement" , "Like some interests" .)