He can't be a keeper! (5)
I believe the answer is:
giver
'a keeper' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'he can't' is the wordplay.
I cannot quite understand how this works, but
'he' could be 'iver' and 'iver' is located in the answer.
A single letter 'g' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'be' acts as a link.
Can you help me to learn more?
(Other definitions for giver that I've seen before include "Present source" , "Bestower" , "Donor" , "presenter" .)