One offering free kebab, say? (5)
I believe the answer is:
donor
'one offering free kebab say?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for donor that I've seen before include "One giving to a cause" , "Supporter" , "One who gives something" , "One contributing" , "Subscriber" .)