A bit of a chump, but you like him (4)
I believe the answer is:
chum
'you like him' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a bit of a chump but' is the wordplay.
'a bit of' says to take the initial letters.
'but' becomes 'hum' (I can't explain this - if you can you should believe this answer much more).
The first letter of 'chump' is 'c'.
'c'+'hum'='CHUM'
Can you help me to learn more?
(Other definitions for chum that I've seen before include "Close friend (colloq.)" , "Informally, a close friend" , "Good friend" , "Pal, mate" , "Pal, buddy" .)