Act as agent concerning gift (9)
I believe the answer is:
represent
'act' is the definition.
(I know that act can be written as represent)
'concerning gift' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'gift' becomes 'present' (present is a kind of gift).
're'+'present'='REPRESENT'
'as agent' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for represent that I've seen before include "Act for" , "Explain" , "Picture" , "Mean" , "show" .)