He's up to it, by all accounts (4)
I believe the answer is:
abel
'he's up to it by all accounts' is the definition.
The definition suggests a singular noun which matches the answer.
'he's up to it by' is the wordplay.
'he' becomes 'abe'.
'up to it' becomes 'l' (I can't justify this - if you can you should give a lot more credence to this answer).
'by' means one lot of letters go next to another.
'abe'+'l'='ABEL'
Can you help me to learn more?
(Other definitions for abel that I've seen before include "The first known murder victim" , "First person killed" , "Old Testament brother" , "character in the Bible" , "Biblical murder victim" .)