He's keen to be seen in rhyme? (5,6)
I believe the answer is:
eager beaver
'he's' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'keen to be seen in rhyme?' is the wordplay.
'keen' becomes 'eager' (I've seen this in another clue).
'to be seen in rhyme?' becomes 'beaver' (I can't justify this - if you can you should believe this answer much more).
'eager'+'beaver'='EAGER BEAVER'
Can you help me to learn more?
(Other definitions for eager beaver that I've seen before include "Enthusiastic worker" , "Alert and active type?" , "very keen type" , "Keen worker" , "Keen person" .)